Going Concern - Additional Information (Detail) - USD ($) $ in Thousands				1 Months Ended	9 Months Ended
	Oct. 16, 2017	Apr. 05, 2017	Apr. 03, 2017	Sep. 30, 2017	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015	Dec. 22, 2015	Jul. 31, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Unrestricted cash and cash equivalents				$ 107,245	$ 107,245	$ 17,200	$ 21,524	$ 36,463	$ 185,606
Special cash dividend distributed		$ 140,000
Dividend payable date		May 26, 2017
Dividend payable, date of record		May 17, 2017
Aggregate principal amount outstanding redeemed					175,000
Convertible Notes [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Interest rate (as a percent)			4.50%								4.50%
Deposited into escrow account			$ 60,000	60,000	$ 60,000
2022 Notes [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Interest rate (as a percent)										11.50%
Asset Sale Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Special cash dividend distributed			$ 140,000
Asset Sale Agreement [Member] | 2022 Notes [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Interest rate (as a percent)			11.50%
Aggregate principal amount outstanding redeemed			$ 175,000
Additional premium payment			20,100
Ipsen [Member] | Asset Sale Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront cash payment received			$ 575,000
Working capital adjustments received				$ 800
Subsequent Event [Member] | Ipsen [Member] | Asset Sale Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Working capital adjustments received	$ 4,900