Summary of Changes in Accounts Receivable and Contract Liabilities (Deferred Revenue) (Detail) - EUSA - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract Liabilities, Transaction Price		$ 12,500	$ 10,500	$ 8,500
Ending Balance March 31, 2020	$ 4,000
Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract Liabilities, Transaction Price	12,500
Beginning Balance January 1, 2020	4,526
Deductions	(493)
Ending Balance March 31, 2020	4,033
Accounting Standards Update 2014-09 | Upfront Payment
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract Liabilities, Transaction Price	$ 2,500
Contract Liabilities, Date Achieved	2015-12
Contract Liabilities Date Paid	2015-12
Beginning Balance January 1, 2020	$ 907
Deductions	(98)
Ending Balance March 31, 2020	809
Accounting Standards Update 2014-09 | R&D Payment - EMA Approval in RCC
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract Liabilities, Transaction Price	$ 4,000
Contract Liabilities, Date Achieved	2017-08
Contract Liabilities Date Paid	2017-09
Beginning Balance January 1, 2020	$ 1,448
Deductions	(158)
Ending Balance March 31, 2020	1,290
Accounting Standards Update 2014-09 | Milestone - UK Reimbursement Approval
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract Liabilities, Transaction Price	$ 2,000
Contract Liabilities, Date Achieved	2018-02
Contract Liabilities Date Paid	2018-03
Beginning Balance January 1, 2020	$ 724
Deductions	(79)
Ending Balance March 31, 2020	645
Accounting Standards Update 2014-09 | Milestone - German Reimbursement Approval
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract Liabilities, Transaction Price	$ 2,000
Contract Liabilities, Date Achieved	2018-11
Contract Liabilities Date Paid	2018-12
Beginning Balance January 1, 2020	$ 723
Deductions	(79)
Ending Balance March 31, 2020	644
Accounting Standards Update 2014-09 | Milestone - Spanish Reimbursement Approval
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract Liabilities, Transaction Price	$ 2,000
Contract Liabilities, Date Achieved	2019-02
Contract Liabilities Date Paid	2019-05
Beginning Balance January 1, 2020	$ 724
Deductions	(79)
Ending Balance March 31, 2020	645
Accounting Standards Update 2014-09 | Accounts Receivable
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Beginning Balance January 1, 2020	270
Additions	291
Ending Balance March 31, 2020	$ 561