Gross-to-Net Product Sales and Significant Customers - Summary of Customers Representing 10% or More of Gross Product Sales (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue, Major Customer [Line Items]
Gross product sales	$ 244,770	$ 215,136	$ 284,685
Oncology Supply, a division of ASD Specialty Healthcare, Inc., and its affiliates (excluding ICS) [Member]
Revenue, Major Customer [Line Items]
Gross product sales	93,951	78,989	115,079
McKesson Corporation and its affiliates [Member]
Revenue, Major Customer [Line Items]
Gross product sales	75,952	73,577	93,656
Cardinal Health, Inc. and its affiliates [Member]
Revenue, Major Customer [Line Items]
Gross product sales	58,780	37,414
All Other Customers [Member]
Revenue, Major Customer [Line Items]
Gross product sales	$ 16,087	$ 25,156	$ 75,950
Customer Concentration Risk [Member] | Gross Product Sales [Member]
Revenue, Major Customer [Line Items]
Percentage of sales	100.00%	100.00%	100.00%
Customer Concentration Risk [Member] | Gross Product Sales [Member] | Oncology Supply, a division of ASD Specialty Healthcare, Inc., and its affiliates (excluding ICS) [Member]
Revenue, Major Customer [Line Items]
Percentage of sales	38.40%	36.70%	40.40%
Customer Concentration Risk [Member] | Gross Product Sales [Member] | McKesson Corporation and its affiliates [Member]
Revenue, Major Customer [Line Items]
Percentage of sales	31.00%	34.20%	32.90%
Customer Concentration Risk [Member] | Gross Product Sales [Member] | Cardinal Health, Inc. and its affiliates [Member]
Revenue, Major Customer [Line Items]
Percentage of sales	24.00%	17.40%	0.00%
Customer Concentration Risk [Member] | Gross Product Sales [Member] | All Other Customers [Member]
Revenue, Major Customer [Line Items]
Percentage of sales	6.60%	11.70%	26.70%
Customer Concentration Risk [Member] | Gross Product Sales [Member] | Maximum [Member] | Integrated Commercialization Solutions, Inc. (ICS) [Member]
Revenue, Major Customer [Line Items]
Percentage of sales		10.00%
Customer Concentration Risk [Member] | Gross Product Sales [Member] | Maximum [Member] | Cardinal Health, Inc. and its affiliates [Member]
Revenue, Major Customer [Line Items]
Percentage of sales	10.00%	10.00%