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Contingent Consideration Receivable

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Janssen Collaboration Agreement (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 13, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue		$ 6,117	$ 8,781	$ 28,572	$ 8,781
Revenue recognized		5,900	0	27,900	0
Deferred revenue - related party		7,970		7,970				$ 31,752
Receivable from collaboration partner - related party		4,586		4,586				1,816
Payable to collaboration partner - related party		764		764
Revenue recognized from performance obligations in previous periods		0	0	0	0
Costs to obtain or fulfill the contract that were capitalized		0	0	0	0
License and Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Development cost	20.00%
Phase 2 clinical trial \| Other services
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue		200	400	700	400
Janssen Biotech, Inc. \| License and Collaborative Revenue
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized		6,100	8,800	28,600	8,800
Janssen Biotech, Inc. \| License and Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue - related party		7,970	41,739	7,970	41,739		$ 13,202	31,752
Payable to collaboration partner - related party		764		764			$ 276
Transaction price recognized based on proportional performance		5,928	$ 8,393	27,929	$ 8,393
Transaction price		56,400		56,400				53,900
Development cost	80.00%
Increase in transaction price				2,500
Janssen Biotech, Inc. \| License and Collaboration Agreement \| Upfront cash payment
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue	$ 50,000
Janssen Biotech, Inc. \| Phase 2 clinical trial
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue				6,400
Janssen Biotech, Inc. \| Payment upon filing IND
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible payment receivable		$ 25,000		$ 25,000				$ 25,000
Janssen Biotech, Inc. \| Forecast \| License and Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of details provided for PTG-200 to prescribers upon commercial launch						30.00%
Janssen Biotech, Inc. \| Forecast \| First Opt-in Election
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Forfeiture of remaining rights and payment of cost, penalty percentage						50.00%
Future opt-in payment eligible to receive under collaboration arrangement						$ 125,000
Janssen Biotech, Inc. \| Forecast \| Second Opt-in Election
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Future opt-in revenue eligible to receive						200,000
Potential development, regulatory and sales milestone payments						$ 590,000