$PRTA
PROTHENA CORP PUBLIC LTD CO Stock $prta

$prta Overview Financials Valuation SEC Filings Company Website

2021 Q4 Form 10-K Financial Statement

#000155905322000008 Filed on February 25, 2022

Income Statement

Concept	2021 Q4	2021	2020 Q4
Revenue	$1.172M	$200.6M	$360.0K
YoY Change	225.56%	23414.3%	40.63%
Cost Of Revenue
YoY Change
Gross Profit
YoY Change
Gross Profit Margin
Selling, General & Admin	$12.21M	$46.32M	$9.910M
YoY Change	23.17%	19.68%	22.95%
% of Gross Profit
Research & Development	$22.06M	$82.28M	$20.76M
YoY Change	6.25%	9.88%	34.2%
% of Gross Profit
Depreciation & Amortization	$240.0K	$1.115M	$360.0K
YoY Change	-33.33%	-26.35%	-10.0%
% of Gross Profit
Operating Expenses	$34.26M	$128.6M	$30.67M
YoY Change	11.73%	13.22%	30.34%
Operating Profit		$71.98M
YoY Change		-163.84%
Interest Expense	$12.00K	$42.00K	$10.00K
YoY Change	20.0%	-96.93%	-99.36%
% of Operating Profit		0.06%
Other Income/Expense, Net	-$16.00K	-$54.00K	-$70.00K
YoY Change	-77.14%	-104.13%	-450.0%
Pretax Income	-$33.10M	$71.92M	-$30.36M
YoY Change	9.01%	-164.55%	39.97%
Income Tax	$83.00K	$4.946M	$350.0K
% Of Pretax Income		6.88%
Net Earnings	-$33.18M	$66.98M	-$30.72M
YoY Change	8.02%	-160.26%	42.51%
Net Earnings / Revenue	-2830.97%	33.39%	-8532.22%
Basic Earnings Per Share		$1.51	-$0.77
Diluted Earnings Per Share	-$711.3K	$1.38	-$0.77
COMMON SHARES
Basic Shares Outstanding	46.59M shares	44.23M shares	39.92M shares
Diluted Shares Outstanding		48.46M shares

Balance Sheet

Concept	2021 Q4	2021	2020 Q4
SHORT-TERM ASSETS
Cash & Short-Term Investments	$579.1M	$579.1M	$295.4M
YoY Change	96.04%	96.04%	-21.37%
Cash & Equivalents	$579.1M	$579.1M	$295.4M
Short-Term Investments
Other Short-Term Assets	$5.715M	$5.715M	$3.900M
YoY Change	46.54%	46.54%	50.93%
Inventory
Prepaid Expenses
Receivables	$0.00	$0.00	$15.00K
Other Receivables	$0.00	$0.00	$0.00
Total Short-Term Assets	$584.8M	$584.8M	$299.3M
YoY Change	95.4%	95.39%	-20.9%
LONG-TERM ASSETS
Property, Plant & Equipment	$2.012M	$14.14M	$2.551M
YoY Change	-21.13%	-30.71%	-34.15%
Goodwill
YoY Change
Intangibles
YoY Change
Long-Term Investments
YoY Change
Other Assets	$1.999M	$10.42M	$333.0K
YoY Change	500.3%	-21.64%	-69.31%
Total Long-Term Assets	$24.56M	$24.56M	$33.69M
YoY Change	-27.11%	-27.13%	-17.61%
TOTAL ASSETS
Total Short-Term Assets	$584.8M	$584.8M	$299.3M
Total Long-Term Assets	$24.56M	$24.56M	$33.69M
Total Assets	$609.4M	$609.4M	$333.0M
YoY Change	83.01%	82.99%	-20.58%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$3.691M	$3.691M	$4.117M
YoY Change	-10.35%	-9.98%	231.48%
Accrued Expenses	$20.94M	$20.94M	$20.50M
YoY Change	2.12%	2.12%	30.57%
Deferred Revenue
YoY Change
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$33.45M	$33.45M	$25.85M
YoY Change	29.42%	29.66%	45.92%
LONG-TERM LIABILITIES
Long-Term Debt	$0.00	$0.00	$0.00
YoY Change
Other Long-Term Liabilities	$553.0K	$109.9M	$553.0K
YoY Change	0.0%	-10.75%	0.0%
Total Long-Term Liabilities	$109.9M	$109.9M	$123.1M
YoY Change	-10.76%	-10.75%	-4.29%
TOTAL LIABILITIES
Total Short-Term Liabilities	$33.45M	$33.45M	$25.85M
Total Long-Term Liabilities	$109.9M	$109.9M	$123.1M
Total Liabilities	$143.3M	$143.3M	$149.0M
YoY Change	-3.79%	-3.81%	1.79%
SHAREHOLDERS EQUITY
Retained Earnings	-$716.1M		-$783.0M
YoY Change	-8.55%		16.54%
Common Stock	$466.0K		$399.0K
YoY Change	16.79%		0.0%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$466.0M	$466.0M	$184.0M
YoY Change
Total Liabilities & Shareholders Equity	$609.4M	$609.4M	$333.0M
YoY Change	83.01%	82.99%	-20.58%

Cashflow Statement

Concept	2021 Q4	2021	2020 Q4
OPERATING ACTIVITIES
Net Income	-$33.18M	$66.98M	-$30.72M
YoY Change	8.02%	-160.26%	42.51%
Depreciation, Depletion And Amortization	$240.0K	$1.115M	$360.0K
YoY Change	-33.33%	-26.35%	-10.0%
Cash From Operating Activities	-$22.46M	$92.61M	-$19.09M
YoY Change	17.64%	-215.23%	31.75%
INVESTING ACTIVITIES
Capital Expenditures	-$319.0K	-$575.0K	-$50.00K
YoY Change	538.0%	187.5%	-54.55%
Acquisitions
YoY Change
Other Investing Activities	$0.00	$0.00	$0.00
YoY Change
Cash From Investing Activities	-$319.0K	-$575.0K	-$50.00K
YoY Change	538.0%	193.37%	-54.55%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net		$78.05M
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	1.773M	$190.3M	0.000
YoY Change		88426.51%	-100.0%
NET CHANGE
Cash From Operating Activities	-22.46M	$92.61M	-19.09M
Cash From Investing Activities	-319.0K	-$575.0K	-50.00K
Cash From Financing Activities	1.773M	$190.3M	0.000
Net Change In Cash	-21.00M	$282.4M	-19.14M
YoY Change	9.74%	-451.45%	31.19%
FREE CASH FLOW
Cash From Operating Activities	-$22.46M	$92.61M	-$19.09M
Capital Expenditures	-$319.0K	-$575.0K	-$50.00K
Free Cash Flow	-$22.14M	$93.18M	-$19.04M
YoY Change	16.28%	-216.24%	32.41%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2021	dei	Amendment Flag AmendmentFlag	false
CY2021	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2021
CY2021	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2021	dei	Entity Central Index Key EntityCentralIndexKey	0001559053
CY2021	dei	Document Type DocumentType	10-K
CY2021	dei	Document Annual Report DocumentAnnualReport	true
CY2021	dei	Document Period End Date DocumentPeriodEndDate	2021-12-31
CY2021	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2021	dei	Document Transition Report DocumentTransitionReport	false
CY2021	dei	Entity File Number EntityFileNumber	001-35676
CY2021	dei	Entity Registrant Name EntityRegistrantName	PROTHENA CORPORATION PUBLIC LIMITED COMPANY
CY2021	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	L2
CY2021	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	98-1111119
CY2021	dei	Entity Address Address Line1 EntityAddressAddressLine1	77 Sir John Rogerson’s Quay, Block C
CY2021	dei	Entity Address Address Line2 EntityAddressAddressLine2	Grand Canal Docklands
CY2021	dei	Entity Address City Or Town EntityAddressCityOrTown	Dublin 2,
CY2021	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	D02 VK60,
CY2021	dei	Entity Address Country EntityAddressCountry	IE
CY2021	dei	Country Region CountryRegion	353
CY2021	dei	City Area Code CityAreaCode	1
CY2021	dei	Local Phone Number LocalPhoneNumber	236-2500
CY2021	dei	Security12b Title Security12bTitle	Ordinary Shares, par value $0.01 per share
CY2021	dei	Trading Symbol TradingSymbol	PRTA
CY2021	dei	Security Exchange Name SecurityExchangeName	NASDAQ
CY2021	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2021	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2021	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2021	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2021	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2021	dei	Entity Small Business EntitySmallBusiness	false
CY2021	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
CY2021	dei	Icfr Auditor Attestation Flag IcfrAuditorAttestationFlag	true
CY2021	dei	Entity Shell Company EntityShellCompany	false
CY2021Q2	dei	Entity Public Float EntityPublicFloat	1727740034	USD
CY2022Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	46685735	shares
CY2021	us-gaap	Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax	-96000	USD
CY2020	us-gaap	Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax	-62000	USD
CY2021Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	579094000	USD
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	295380000	USD
CY2021Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	0	USD
CY2020Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	15000	USD
CY2021Q4	us-gaap	Prepaid Expense And Other Assets Current PrepaidExpenseAndOtherAssetsCurrent	5715000	USD
CY2020Q4	us-gaap	Prepaid Expense And Other Assets Current PrepaidExpenseAndOtherAssetsCurrent	2537000	USD
CY2021Q4	us-gaap	Restricted Cash Current RestrictedCashCurrent	0	USD
CY2020Q4	us-gaap	Restricted Cash Current RestrictedCashCurrent	1352000	USD
CY2021Q4	us-gaap	Assets Current AssetsCurrent	584809000	USD
CY2020Q4	us-gaap	Assets Current AssetsCurrent	299284000	USD
CY2021Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	2012000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	2551000	USD
CY2021Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	12123000	USD
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	17811000	USD
CY2021Q4	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	7071000	USD
CY2020Q4	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	11644000	USD
CY2021Q4	us-gaap	Restricted Cash Noncurrent RestrictedCashNoncurrent	1352000	USD
CY2020Q4	us-gaap	Restricted Cash Noncurrent RestrictedCashNoncurrent	1352000	USD
CY2021Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	1999000	USD
CY2020Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	333000	USD
CY2021Q4	us-gaap	Assets Noncurrent AssetsNoncurrent	24557000	USD
CY2020Q4	us-gaap	Assets Noncurrent AssetsNoncurrent	33691000	USD
CY2021Q4	us-gaap	Assets Assets	609366000	USD
CY2020Q4	us-gaap	Assets Assets	332975000	USD
CY2021Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	3691000	USD
CY2020Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	4117000	USD
CY2021Q4	prta	Accrued Research And Development Current AccruedResearchAndDevelopmentCurrent	6351000	USD
CY2020Q4	prta	Accrued Research And Development Current AccruedResearchAndDevelopmentCurrent	9044000	USD
CY2021Q4	us-gaap	Accrued Income Taxes Current AccruedIncomeTaxesCurrent	0	USD
CY2020Q4	us-gaap	Liabilities Noncurrent LiabilitiesNoncurrent	123121000	USD
CY2020Q4	us-gaap	Accrued Income Taxes Current AccruedIncomeTaxesCurrent	36000	USD
CY2021Q4	us-gaap	Deferred Revenue Current DeferredRevenueCurrent	7657000	USD
CY2020Q4	us-gaap	Deferred Revenue Current DeferredRevenueCurrent	0	USD
CY2021Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	5940000	USD
CY2020Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	5512000	USD
CY2021Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	9813000	USD
CY2020Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	7139000	USD
CY2021Q4	us-gaap	Liabilities Current LiabilitiesCurrent	33452000	USD
CY2020Q4	us-gaap	Liabilities Current LiabilitiesCurrent	25848000	USD
CY2021Q4	us-gaap	Deferred Revenue Noncurrent DeferredRevenueNoncurrent	102933000	USD
CY2020Q4	us-gaap	Deferred Revenue Noncurrent DeferredRevenueNoncurrent	110242000	USD
CY2021Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	6386000	USD
CY2020Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	12326000	USD
CY2021Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	553000	USD
CY2020Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	553000	USD
CY2021Q4	us-gaap	Liabilities Noncurrent LiabilitiesNoncurrent	109872000	USD
CY2021Q4	us-gaap	Liabilities Liabilities	143324000	USD
CY2020Q4	us-gaap	Liabilities Liabilities	148969000	USD
CY2021Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2020Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2020Q4	prta	Deferred Shares Par Value DeferredSharesParValue	22
CY2021Q4	prta	Deferred Shares Par Value DeferredSharesParValue	22
CY2021Q4	prta	Deferred Shares Value DeferredSharesValue	0	USD
CY2020Q4	prta	Deferred Shares Value DeferredSharesValue	0	USD
CY2020Q4	prta	Deferred Shares Shares Authorized DeferredSharesSharesAuthorized	10000	shares
CY2021Q4	prta	Deferred Shares Shares Authorized DeferredSharesSharesAuthorized	10000	shares
CY2020Q4	prta	Deferred Shares Shares Authorized DeferredSharesSharesAuthorized	10000	shares
CY2021Q4	prta	Deferred Shares Shares Authorized DeferredSharesSharesAuthorized	10000	shares
CY2020Q4	prta	Deferred Shares Shares Outstanding DeferredSharesSharesOutstanding	0	shares
CY2021Q4	prta	Deferred Shares Shares Issued DeferredSharesSharesIssued	0	shares
CY2021Q4	prta	Deferred Shares Shares Outstanding DeferredSharesSharesOutstanding	0	shares
CY2020Q4	prta	Deferred Shares Shares Issued DeferredSharesSharesIssued	0	shares
CY2020Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2021Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2021Q4	us-gaap	Common Stock Value CommonStockValue	466000	USD
CY2020Q4	us-gaap	Common Stock Value CommonStockValue	399000	USD
CY2021Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	100000000	shares
CY2020Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	100000000	shares
CY2021Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	46660294	shares
CY2021Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	46660294	shares
CY2020Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	39921413	shares
CY2020Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	39921413	shares
CY2021Q4	us-gaap	Additional Paid In Capital AdditionalPaidInCapital	1181630000	USD
CY2020Q4	us-gaap	Additional Paid In Capital AdditionalPaidInCapital	966636000	USD
CY2021Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	-716054000	USD
CY2020Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	-783029000	USD
CY2021Q4	us-gaap	Stockholders Equity StockholdersEquity	466042000	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	184006000	USD
CY2021Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	609366000	USD
CY2020Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	332975000	USD
CY2021	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	200577000	USD
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	853000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	814000	USD
CY2021	us-gaap	Research And Development Expense ResearchAndDevelopmentExpense	82284000	USD
CY2020	us-gaap	Research And Development Expense ResearchAndDevelopmentExpense	74884000	USD
CY2019	us-gaap	Research And Development Expense ResearchAndDevelopmentExpense	50836000	USD
CY2021	us-gaap	General And Administrative Expense GeneralAndAdministrativeExpense	46318000	USD
CY2020	us-gaap	General And Administrative Expense GeneralAndAdministrativeExpense	38703000	USD
CY2019	us-gaap	General And Administrative Expense GeneralAndAdministrativeExpense	35736000	USD
CY2021	us-gaap	Restructuring Costs RestructuringCosts	0	USD
CY2020	us-gaap	Restructuring Costs RestructuringCosts	0	USD
CY2019	us-gaap	Restructuring Costs RestructuringCosts	-61000	USD
CY2021	us-gaap	Operating Expenses OperatingExpenses	128602000	USD
CY2020	us-gaap	Operating Expenses OperatingExpenses	113587000	USD
CY2019	us-gaap	Operating Expenses OperatingExpenses	86511000	USD
CY2021	us-gaap	Operating Income Loss OperatingIncomeLoss	71975000	USD
CY2020	us-gaap	Operating Income Loss OperatingIncomeLoss	-112734000	USD
CY2019	us-gaap	Operating Income Loss OperatingIncomeLoss	-85697000	USD
CY2021	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	42000	USD
CY2020	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	1369000	USD
CY2019	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	8203000	USD
CY2021	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	-96000	USD
CY2020	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	-62000	USD
CY2019	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	196000	USD
CY2021	us-gaap	Nonoperating Income Expense NonoperatingIncomeExpense	-54000	USD
CY2020	us-gaap	Nonoperating Income Expense NonoperatingIncomeExpense	1307000	USD
CY2019	us-gaap	Nonoperating Income Expense NonoperatingIncomeExpense	8399000	USD
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	71921000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-111427000	USD
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CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4946000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-283000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	379000	USD
CY2021	us-gaap	Net Income Loss NetIncomeLoss	66975000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	-111144000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	-77677000	USD
CY2021	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.51
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-2.78
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-1.95
CY2021	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.38
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-2.78
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-1.95
CY2021	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	44228000	shares
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	39915000	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	39882000	shares
CY2021	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	48464000	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	39915000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	39882000	shares
CY2021	us-gaap	Net Income Loss NetIncomeLoss	66975000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	-111144000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	-77677000	USD
CY2021	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	1115000	USD
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CY2019	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	1564000	USD
CY2021	prta	Sharebased Compensationnonrestructuring SharebasedCompensationnonrestructuring	24658000	USD
CY2020	prta	Sharebased Compensationnonrestructuring SharebasedCompensationnonrestructuring	22014000	USD
CY2019	prta	Sharebased Compensationnonrestructuring SharebasedCompensationnonrestructuring	23585000	USD
CY2021	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	4573000	USD
CY2020	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	-1688000	USD
CY2019	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	-1248000	USD
CY2021	prta	Amortizationofrightofuseasset Amortizationofrightofuseasset	5688000	USD
CY2020	prta	Amortizationofrightofuseasset Amortizationofrightofuseasset	5463000	USD
CY2019	prta	Amortizationofrightofuseasset Amortizationofrightofuseasset	5256000	USD
CY2021	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	-15000	USD
CY2020	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	-53000	USD
CY2019	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	0	USD
CY2021	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	4763000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	-799000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	-807000	USD
CY2021	us-gaap	Increase Decrease In Deferred Revenue IncreaseDecreaseInDeferredRevenue	348000	USD
CY2020	us-gaap	Increase Decrease In Deferred Revenue IncreaseDecreaseInDeferredRevenue	0	USD
CY2019	us-gaap	Increase Decrease In Deferred Revenue IncreaseDecreaseInDeferredRevenue	0	USD
CY2021	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	-492000	USD
CY2020	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	7728000	USD
CY2019	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	-78000	USD
CY2021	us-gaap	Increase Decrease In Restructuring Reserve IncreaseDecreaseInRestructuringReserve	0	USD
CY2020	us-gaap	Increase Decrease In Restructuring Reserve IncreaseDecreaseInRestructuringReserve	0	USD
CY2019	us-gaap	Increase Decrease In Restructuring Reserve IncreaseDecreaseInRestructuringReserve	-461000	USD
CY2021	us-gaap	Increase Decrease In Operating Lease Liability IncreaseDecreaseInOperatingLeaseLiability	-5512000	USD
CY2020	us-gaap	Increase Decrease In Operating Lease Liability IncreaseDecreaseInOperatingLeaseLiability	-5101000	USD
CY2019	us-gaap	Increase Decrease In Operating Lease Liability IncreaseDecreaseInOperatingLeaseLiability	-4717000	USD
CY2021	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	92605000	USD
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	-80362000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	-52969000	USD
CY2021	us-gaap	Payments To Acquire Machinery And Equipment PaymentsToAcquireMachineryAndEquipment	575000	USD
CY2020	us-gaap	Payments To Acquire Machinery And Equipment PaymentsToAcquireMachineryAndEquipment	196000	USD
CY2019	us-gaap	Payments To Acquire Machinery And Equipment PaymentsToAcquireMachineryAndEquipment	555000	USD
CY2021	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	0	USD
CY2020	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	0	USD
CY2019	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	8000	USD
CY2021	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-575000	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-196000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-547000	USD
CY2021	prta	Proceeds From Issuance Of Ordinary Shares In At The Market Offering Net ProceedsFromIssuanceOfOrdinarySharesInAtTheMarketOfferingNet	96739000	USD
CY2021	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	78049000	USD
CY2020	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	0	USD
CY2019	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	0	USD
CY2020	prta	Proceeds From Issuance Of Ordinary Shares In At The Market Offering Net ProceedsFromIssuanceOfOrdinarySharesInAtTheMarketOfferingNet	0	USD
CY2019	prta	Proceeds From Issuance Of Ordinary Shares In At The Market Offering Net ProceedsFromIssuanceOfOrdinarySharesInAtTheMarketOfferingNet	0	USD
CY2021	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	15544000	USD
CY2020	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	215000	USD
CY2019	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	228000	USD
CY2021	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	190332000	USD
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	215000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	228000	USD
CY2021	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect	282362000	USD
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect	-80343000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect	-53288000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	298084000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	378427000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	431715000	USD
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	580446000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	298084000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	378427000	USD
CY2021	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	580000	USD
CY2020	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	1367000	USD
CY2019	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	1580000	USD
CY2021	prta	Non Cash Financing Receivable From Option Exercises NonCashFinancingReceivableFromOptionExercises	13000	USD
CY2020	prta	Non Cash Financing Receivable From Option Exercises NonCashFinancingReceivableFromOptionExercises	0	USD
CY2019	prta	Non Cash Financing Receivable From Option Exercises NonCashFinancingReceivableFromOptionExercises	0	USD
CY2021	us-gaap	Noncash Or Part Noncash Acquisition Fixed Assets Acquired1 NoncashOrPartNoncashAcquisitionFixedAssetsAcquired1	0	USD
CY2020	us-gaap	Noncash Or Part Noncash Acquisition Fixed Assets Acquired1 NoncashOrPartNoncashAcquisitionFixedAssetsAcquired1	0	USD
CY2019	us-gaap	Noncash Or Part Noncash Acquisition Fixed Assets Acquired1 NoncashOrPartNoncashAcquisitionFixedAssetsAcquired1	5000	USD
CY2021	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	0	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	0	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	28530000	USD
CY2021	prta	Reductionof Buildtosuit Lease Obligation ReductionofBuildtosuitLeaseObligation	0	USD
CY2020	prta	Reductionof Buildtosuit Lease Obligation ReductionofBuildtosuitLeaseObligation	0	USD
CY2019	prta	Reductionof Buildtosuit Lease Obligation ReductionofBuildtosuitLeaseObligation	-51546000	USD
CY2021	prta	Reductionof Amounts Capitalized Under Buildtosuit Lease Transaction ReductionofAmountsCapitalizedUnderBuildtosuitLeaseTransaction	0	USD
CY2020	prta	Reductionof Amounts Capitalized Under Buildtosuit Lease Transaction ReductionofAmountsCapitalizedUnderBuildtosuitLeaseTransaction	0	USD
CY2019	prta	Reductionof Amounts Capitalized Under Buildtosuit Lease Transaction ReductionofAmountsCapitalizedUnderBuildtosuitLeaseTransaction	-46760000	USD
CY2021	prta	Reductionof Capitalized Interest During Construction Periodfor Buildtosuit Lease Transaction ReductionofCapitalizedInterestDuringConstructionPeriodforBuildtosuitLeaseTransaction	0	USD
CY2020	prta	Reductionof Capitalized Interest During Construction Periodfor Buildtosuit Lease Transaction ReductionofCapitalizedInterestDuringConstructionPeriodforBuildtosuitLeaseTransaction	0	USD
CY2019	prta	Reductionof Capitalized Interest During Construction Periodfor Buildtosuit Lease Transaction ReductionofCapitalizedInterestDuringConstructionPeriodforBuildtosuitLeaseTransaction	-1099000	USD
CY2021Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	579094000	USD
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	295380000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	375723000	USD
CY2021Q4	us-gaap	Restricted Cash Current RestrictedCashCurrent	0	USD
CY2020Q4	us-gaap	Restricted Cash Current RestrictedCashCurrent	1352000	USD
CY2019Q4	us-gaap	Restricted Cash Current RestrictedCashCurrent	0	USD
CY2020Q4	us-gaap	Restricted Cash Noncurrent RestrictedCashNoncurrent	1352000	USD
CY2019Q4	us-gaap	Restricted Cash Noncurrent RestrictedCashNoncurrent	2704000	USD
CY2021Q4	us-gaap	Restricted Cash Noncurrent RestrictedCashNoncurrent	1352000	USD
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	580446000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	298084000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	378427000	USD
CY2018Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	322998000	USD
CY2019	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	23585000	USD
CY2019	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	228000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	-77677000	USD
CY2019Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	272921000	USD
CY2020	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	22014000	USD
CY2020	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	215000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	-111144000	USD
CY2020Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	184006000	USD
CY2021	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	24658000	USD
CY2021	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	15557000	USD
CY2021	us-gaap	Net Income Loss NetIncomeLoss	66975000	USD
CY2021Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	466042000	USD
CY2021Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	-716100000	USD
CY2021Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	579100000	USD
CY2021	us-gaap	Use Of Estimates UseOfEstimates	<div style="margin-top:9pt;text-indent:9pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Use of Estimates</span></div><div style="margin-top:10pt;text-align:justify;text-indent:24.75pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The preparation of the Consolidated Financial Statements in conformity with GAAP requires management to make judgments, estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosures. On an ongoing basis, management evaluates its estimates, including critical accounting policies or estimates related to revenue recognition, share-based compensation, research and development expenses and leases. The Company bases its estimates on historical experience and on various other market specific and other relevant assumptions that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Because of the uncertainties inherent in such estimates, actual results may differ materially from these estimates.</span></div>
CY2021	us-gaap	Concentration Risk Credit Risk ConcentrationRiskCreditRisk	<div style="margin-top:10pt;text-align:justify;text-indent:24.75pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Financial instruments that potentially subject the Company to concentration of credit risk consist of cash and cash equivalents and accounts receivable. The Company places its cash equivalents with high credit quality financial institutions and, by policy, limits the amount of credit exposure with any one financial institution. Deposits held with banks may exceed the amount of insurance provided on such deposits. The Company has not experienced any losses on its deposits of cash and cash equivalents and its credit risk exposure is up to the extent recorded on the Company's Consolidated Balance Sheet.</span></div><div style="margin-top:10pt;text-align:justify;text-indent:24.75pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">There were no receivables recorded in the Consolidated Balance Sheet as of December 31, 2021. The Company's credit risk exposure is up to the extent recorded on the Company's Consolidated Balance Sheet.</span></div><div style="margin-top:10pt;text-align:justify;text-indent:24.75pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> The Company’s business is primarily conducted in U.S. dollars except for its agreements with contract manufacturers for drug supplies which are denominated in Euros. The Company recorded a loss on foreign currency exchange rate differences of approximately $96,000 and $62,000 during the years ended December 31, 2021 and 2020, respectively. If the Company increases its business activities that require the use of foreign currencies, it may be exposed to losses if the Euro and other such currencies continue to strengthen against the U.S. dollar.</span></div><div style="margin-top:10pt;text-align:justify;text-indent:24.75pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">As of December 31, 2021, and 2020, $2.0 million and $2.6 million, respectively, of the Company’s property and equipment, net were held in the U.S. and a nominal amount were in Ireland. </span></div><div style="margin-top:9pt;text-align:justify;text-indent:22.5pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The Company does not own or operate facilities for the manufacture, packaging, labeling, storage, testing or distribution of nonclinical or clinical supplies of any of its drug candidates. The Company instead contracts with and relies on third-parties to manufacture, package, label, store, test and distribute all preclinical development and clinical supplies of our drug candidates, and it plans to continue to do so for the foreseeable future. The Company also relies on third-party consultants to assist in managing these third-parties and assist with its manufacturing strategy.</span></div>
CY2021	us-gaap	Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax	-96000	USD
CY2020	us-gaap	Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax	-62000	USD
CY2021Q4	us-gaap	Machinery And Equipment Gross MachineryAndEquipmentGross	9758000	USD
CY2020Q4	us-gaap	Machinery And Equipment Gross MachineryAndEquipmentGross	9343000	USD
CY2021Q4	us-gaap	Leasehold Improvements Gross LeaseholdImprovementsGross	1393000	USD
CY2020Q4	us-gaap	Leasehold Improvements Gross LeaseholdImprovementsGross	1278000	USD
CY2021Q4	us-gaap	Capitalized Computer Software Gross CapitalizedComputerSoftwareGross	1322000	USD
CY2020Q4	us-gaap	Capitalized Computer Software Gross CapitalizedComputerSoftwareGross	1423000	USD
CY2021Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	12473000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	12044000	USD
CY2021Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	10461000	USD
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	9493000	USD
CY2021Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	2012000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	2551000	USD
CY2021	us-gaap	Depreciation Depreciation	1100000	USD
CY2020	us-gaap	Depreciation Depreciation	1500000	USD
CY2019	us-gaap	Depreciation Depreciation	1600000	USD
CY2021Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	8644000	USD
CY2020Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	5927000	USD
CY2021Q4	us-gaap	Accrued Professional Fees Current AccruedProfessionalFeesCurrent	764000	USD
CY2020Q4	us-gaap	Accrued Professional Fees Current AccruedProfessionalFeesCurrent	696000	USD
CY2021Q4	us-gaap	Other Sundry Liabilities Current OtherSundryLiabilitiesCurrent	405000	USD
CY2020Q4	us-gaap	Other Sundry Liabilities Current OtherSundryLiabilitiesCurrent	516000	USD
CY2021Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	9813000	USD
CY2020Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	7139000	USD
CY2021	us-gaap	Net Income Loss NetIncomeLoss	66975000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	-111144000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	-77677000	USD
CY2021	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	44228000	shares
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	39915000	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	39882000	shares
CY2021	us-gaap	Incremental Common Shares Attributable To Nonvested Shares With Forfeitable Dividends IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends	4236000	shares
CY2020	us-gaap	Incremental Common Shares Attributable To Nonvested Shares With Forfeitable Dividends IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends	0	shares
CY2019	us-gaap	Incremental Common Shares Attributable To Nonvested Shares With Forfeitable Dividends IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends	0	shares
CY2021	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	48464000	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	39915000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	39882000	shares
CY2021	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.51
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-2.78
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	-1.95
CY2021	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.38
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-2.78
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	-1.95
CY2016Q1	prta	Operating Lease Area OperatingLeaseArea	128751	sqft
CY2021Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P2Y
CY2016Q1	us-gaap	Lease Expiration Date1 LeaseExpirationDate1	2023-12-31
CY2016Q2	us-gaap	Capital Leases Future Minimum Payments Due CapitalLeasesFutureMinimumPaymentsDue	39200000	USD
CY2021	us-gaap	Operating Lease Cost OperatingLeaseCost	6300000	USD
CY2020	us-gaap	Operating Lease Cost OperatingLeaseCost	6300000	USD
CY2019	us-gaap	Operating Lease Cost OperatingLeaseCost	6400000	USD
CY2021	us-gaap	Operating Lease Payments OperatingLeasePayments	6200000	USD
CY2020	us-gaap	Operating Lease Payments OperatingLeasePayments	6000000	USD
CY2021Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0425
CY2016Q4	prta	Operating Leases Improvement Allowance OperatingLeasesImprovementAllowance	14200000	USD
CY2018Q3	prta	Operating Leases Sublease Rentals Areaof Sublease Rental OperatingLeasesSubleaseRentalsAreaofSubleaseRental	46641	sqft
CY2021	us-gaap	Sublease Income SubleaseIncome	2900000	USD
CY2020	us-gaap	Sublease Income SubleaseIncome	2900000	USD
CY2019	us-gaap	Sublease Income SubleaseIncome	2900000	USD
CY2018Q3	prta	Subleaserentals Annual Base Rent Initial Amount SubleaserentalsAnnualBaseRentInitialAmount	2700000	USD
CY2018Q3	prta	Operating Leases Sublease Rentals Percent Annual Rent Increase OperatingLeasesSubleaseRentalsPercentAnnualRentIncrease	0.035
CY2018Q3	prta	Operating Leases Sublease Rentals Termof Contract OperatingLeasesSubleaseRentalsTermofContract	P5Y2M12D
CY2018Q3	prta	Operating Leases Sublease Rentals Percentof Rental Gain Attributableto Sublandlord OperatingLeasesSubleaseRentalsPercentofRentalGainAttributabletoSublandlord	0.50
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	6422000	USD
CY2021Q4	us-gaap	Lessor Operating Lease Payments To Be Received Next Twelve Months LessorOperatingLeasePaymentsToBeReceivedNextTwelveMonths	3047000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	6535000	USD
CY2021Q4	us-gaap	Lessor Operating Lease Payments To Be Received Two Years LessorOperatingLeasePaymentsToBeReceivedTwoYears	3019000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	0	USD
CY2021Q4	us-gaap	Lessor Operating Lease Payments To Be Received Three Years LessorOperatingLeasePaymentsToBeReceivedThreeYears	0	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	0	USD
CY2021Q4	us-gaap	Lessor Operating Lease Payments To Be Received Four Years LessorOperatingLeasePaymentsToBeReceivedFourYears	0	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	0	USD
CY2021Q4	us-gaap	Lessor Operating Lease Payments To Be Received Five Years LessorOperatingLeasePaymentsToBeReceivedFiveYears	0	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	12957000	USD
CY2021Q4	us-gaap	Lessor Operating Lease Payments To Be Received LessorOperatingLeasePaymentsToBeReceived	6066000	USD
CY2021Q4	prta	Purchase And Contractual Obligation Due In Year One PurchaseAndContractualObligationDueInYearOne	12319000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	559000	USD
CY2021Q4	prta	Lessee Operating Lease Liability Nominal Payments LesseeOperatingLeaseLiabilityNominalPayments	-72000	USD
CY2021Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	12326000	USD
CY2021Q4	us-gaap	Purchase Obligation PurchaseObligation	12200000	USD
CY2021Q4	us-gaap	Contractual Obligation ContractualObligation	500000	USD
CY2021Q4	us-gaap	Purchase Obligation PurchaseObligation	12178000	USD
CY2021Q4	us-gaap	Purchase Obligation Due In Next Twelve Months PurchaseObligationDueInNextTwelveMonths	12178000	USD
CY2021Q4	us-gaap	Purchase Obligation Due In Second Year PurchaseObligationDueInSecondYear	0	USD
CY2021Q4	us-gaap	Purchase Obligation Due In Third Year PurchaseObligationDueInThirdYear	0	USD
CY2021Q4	us-gaap	Purchase Obligation Due In Fourth Year PurchaseObligationDueInFourthYear	0	USD
CY2021Q4	us-gaap	Purchase Obligation Due In Fifth Year PurchaseObligationDueInFifthYear	0	USD
CY2021Q4	us-gaap	Purchase Obligation Due After Fifth Year PurchaseObligationDueAfterFifthYear	0	USD
CY2021Q4	prta	Purchaseand Contractual Obligation Total PurchaseandContractualObligationTotal	12656000	USD
CY2021Q4	prta	Purchaseand Contractual Obligation Duein Second Year PurchaseandContractualObligationDueinSecondYear	59000	USD
CY2021Q4	prta	Purchaseand Contractual Obligation Duein Third Year PurchaseandContractualObligationDueinThirdYear	49000	USD
CY2021Q4	prta	Purchaseand Contractual Obligation Duein Fourth Year PurchaseandContractualObligationDueinFourthYear	49000	USD
CY2021Q4	prta	Purchaseand Contractual Obligation Duein Fifth Year PurchaseandContractualObligationDueinFifthYear	45000	USD
CY2021Q4	prta	Purchaseand Contractual Obligation Due After Fifth Year PurchaseandContractualObligationDueAfterFifthYear	135000	USD
CY2021Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	100000000	shares
CY2021Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2021Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	46660294	shares
CY2021Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	46660294	shares
CY2021	prta	Numberof Votes NumberofVotes	1	vote
CY2021Q4	prta	Deferred Shares Shares Authorized DeferredSharesSharesAuthorized	10000	shares
CY2021Q4	prta	Deferred Shares Par Value DeferredSharesParValue	22
CY2021Q4	prta	Deferred Shares Share Outstanding DeferredSharesShareOutstanding	0	shares
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod	3530477	shares
CY2021Q1	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	1372587	shares
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod	2108950	shares
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod	1315975	shares
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Period1 ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1	P4Y
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant	3131355	shares
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	8684322	shares
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	19.20
CY2021Q1	prta	Number Of Ordinary Shares Tendered For Exchange Under The Option Exchage NumberOfOrdinarySharesTenderedForExchangeUnderTheOptionExchage	2100000	shares
CY2021Q1	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	22.85
CY2021Q1	prta	Share Based Compensation Arrangement By Share Based Payment Award Options Minimum Exchange Threshold Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsMinimumExchangeThresholdExercisePrice	17.63
CY2021Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Stock Options EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions	51500000	USD
CY2021	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1	P1Y10M20D
CY2021	us-gaap	Share Based Compensation ShareBasedCompensation	24658000	USD
CY2020	us-gaap	Share Based Compensation ShareBasedCompensation	22014000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	23585000	USD
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate	0.817
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate	0.809
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate	0.814
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate	0.010
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate	0.009
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate	0.023
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate	0
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate	0
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate	0
CY2021	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1	P6Y
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1	P6Y
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1	P6Y
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	21.39
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	8.12
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	8.55
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	8744765	shares
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	20.42
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P7Y2M8D
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	4656000	USD
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	3530477	shares
CY2021	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	27.72
CY2021	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	1073707	shares
CY2021	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	14.49
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod	513225	shares
CY2021	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Forfeitures In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice	23.48
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Expirations In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod	2003988	shares
CY2021	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Expirations In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice	40.98
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	8684322	shares
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	19.20
CY2021	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P6Y11M23D
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	269182000	USD
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber	8335615	shares
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice	18.91
CY2021	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm1	P6Y10M24D
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Aggregate Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue	260133000	USD
CY2021	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested Number Of Shares SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares	3659001	shares
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice	14.13
CY2021	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1	P6Y25D
CY2021Q4	prta	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value Related To Vested Options ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValueRelatedToVestedOptions	129217000	USD
CY2021Q1	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	1372587	shares
CY2021Q1	prta	Share Based Compensation Arrangement By Share Based Payment Award Unvested Options Forfeitures In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardUnvestedOptionsForfeituresInPeriod	179959	shares
CY2021Q1	prta	Share Based Compensation Arrangement By Share Based Payment Award Unvested Options Expirations In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardUnvestedOptionsExpirationsInPeriod	1934446	shares
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	71921000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-111427000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	-77298000	USD
CY2021	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	372000	USD
CY2020	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	1405000	USD
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	1628000	USD
CY2021	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	4574000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-1688000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-1249000	USD
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4946000	USD
CY2021	prta	Share Based Compensation Net Tax Shortfall Windfall Amount Booked To Income Tax Provision ShareBasedCompensationNetTaxShortfallWindfallAmountBookedToIncomeTaxProvision	-2300000	USD
CY2020	prta	Share Based Compensation Net Tax Shortfall Windfall Amount Booked To Income Tax Provision ShareBasedCompensationNetTaxShortfallWindfallAmountBookedToIncomeTaxProvision	1000000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-283000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	379000	USD
CY2019	prta	Share Based Compensation Net Tax Shortfall Windfall Amount Booked To Income Tax Provision ShareBasedCompensationNetTaxShortfallWindfallAmountBookedToIncomeTaxProvision	2600000	USD
CY2021	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	8990000	USD
CY2020	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	-13928000	USD
CY2019	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	-9662000	USD
CY2021	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	-398000	USD
CY2020	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	-3402000	USD
CY2019	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	-1202000	USD
CY2021	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	4108000	USD
CY2020	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	16266000	USD
CY2019	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	8248000	USD
CY2021	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	5173000	USD
CY2020	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	3409000	USD
CY2019	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	4518000	USD
CY2021	us-gaap	Income Tax Reconciliation Tax Credits Research IncomeTaxReconciliationTaxCreditsResearch	5355000	USD
CY2020	us-gaap	Income Tax Reconciliation Tax Credits Research IncomeTaxReconciliationTaxCreditsResearch	2786000	USD
CY2019	us-gaap	Income Tax Reconciliation Tax Credits Research IncomeTaxReconciliationTaxCreditsResearch	1470000	USD
CY2021	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	7587000	USD
CY2020	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	0	USD
CY2019	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	0	USD
CY2021	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	15000	USD
CY2020	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	158000	USD
CY2019	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-53000	USD
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	4946000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-283000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	379000	USD
CY2021Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	115424000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	118976000	USD
CY2021Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards Research DeferredTaxAssetsTaxCreditCarryforwardsResearch	17552000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards Research DeferredTaxAssetsTaxCreditCarryforwardsResearch	14804000	USD
CY2021Q4	prta	Deferred Tax Assets Lease Liabilities DeferredTaxAssetsLeaseLiabilities	2670000	USD
CY2020Q4	prta	Deferred Tax Assets Lease Liabilities DeferredTaxAssetsLeaseLiabilities	4199000	USD
CY2021Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals DeferredTaxAssetsTaxDeferredExpenseReservesAndAccruals	1017000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals DeferredTaxAssetsTaxDeferredExpenseReservesAndAccruals	2936000	USD
CY2021Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	7114000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	13048000	USD
CY2021Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	143777000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	153963000	USD
CY2021Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	133845000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	137809000	USD
CY2021Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	9932000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	16154000	USD
CY2021Q4	prta	Deferred Tax Liabilities Operating Lease Rightof Use Assets DeferredTaxLiabilitiesOperatingLeaseRightofUseAssets	2626000	USD
CY2020Q4	prta	Deferred Tax Liabilities Operating Lease Rightof Use Assets DeferredTaxLiabilitiesOperatingLeaseRightofUseAssets	4192000	USD
CY2021Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	235000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	318000	USD
CY2021Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	7071000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	11644000	USD
CY2021	prta	Deferred Tax Assets Period Increase Decrease DeferredTaxAssetsPeriodIncreaseDecrease	-4600000	USD
CY2021	prta	Deferred Tax Assets Period Increase Decrease Tax Cuts And Jobs Act DeferredTaxAssetsPeriodIncreaseDecreaseTaxCutsAndJobsAct	-3500000	USD
CY2021	prta	Deferred Tax Asset Period Increase Decrease American Rescue Plan Act DeferredTaxAssetPeriodIncreaseDecreaseAmericanRescuePlanAct	-1000000	USD
CY2021Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	133800000	USD
CY2021Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	7100000	USD
CY2021	us-gaap	Valuation Allowance Deferred Tax Asset Change In Amount ValuationAllowanceDeferredTaxAssetChangeInAmount	-4000000	USD
CY2021	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	1342000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	703000	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	7252000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	6601000	USD
CY2021	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	0	USD
CY2020	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	124000	USD
CY2021	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	265000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	176000	USD
CY2021Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	8329000	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	7252000	USD
CY2021	dei	Auditor Name AuditorName	KPMG LLP
CY2021	dei	Auditor Location AuditorLocation	San Francisco, CA
CY2021	dei	Auditor Firm AuditorFirmId	185

Files In Submission

Name	View Source	Status
0001559053-22-000008-index-headers.html	Edgar Link	pending
0001559053-22-000008-index.html	Edgar Link	pending
0001559053-22-000008.txt	Edgar Link	pending
0001559053-22-000008-xbrl.zip	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
MetaLinks.json	Edgar Link	pending
prta-20211231.htm	Edgar Link	pending
prta-20211231.xsd	Edgar Link	pending
prta-20211231_cal.xml	Edgar Link	unprocessable
prta-20211231_def.xml	Edgar Link	unprocessable
prta-20211231_g1.jpg	Edgar Link	pending
prta-20211231_g2.jpg	Edgar Link	pending
prta-20211231_htm.xml	Edgar Link	completed
prta-20211231_lab.xml	Edgar Link	unprocessable
prta-20211231_pre.xml	Edgar Link	unprocessable
prta2021ex211listofsubsidi.htm	Edgar Link	pending
prta2021q410-kxex311.htm	Edgar Link	pending
prta2021q410-kxex312.htm	Edgar Link	pending
prta2021q410-kxex321.htm	Edgar Link	pending
prta2021q4ex1020prtaxfirst.htm	Edgar Link	pending
prta2021xex231consentofind.htm	Edgar Link	pending
prta2021xex42descriptionof.htm	Edgar Link	pending
R1.htm	Edgar Link	pending
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R9.htm	Edgar Link	pending
report.css	Edgar Link	pending
Show.js	Edgar Link	pending

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$PRTA
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2021 Q4 Form 10-K Financial Statement

#000155905322000008 Filed on February 25, 2022

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Facts In Submission

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$PRTA PROTHENA CORP PUBLIC LTD CO Stock $prta

2021 Q4 Form 10-K Financial Statement

#000155905322000008 Filed on February 25, 2022

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$PRTA
PROTHENA CORP PUBLIC LTD CO Stock $prta