Marketing and Supply Agreement with Eisai - Revenues Recognized under Collaboration with Eisai (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Net product sales	$ 3,518	$ 6,618
Total revenues	9,847	12,256
Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Net product sales	2,459	4,436
Amortization of upfront payments	1,885	1,885
Subtotal other Eisai collaborative revenue	3,226	2,136
Total revenues	5,685	6,572
Eisai | Research and development
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reimbursement of expenses	1,231	191
Eisai | Patent and trademark expenses
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reimbursement of expenses	$ 110	$ 60