Selected Quarterly Financial Data (Unaudited) - Accounts Receivable Allowances - Summary of Adjustments to Gross Sales (Details) - USD ($) $ in Thousands	3 Months Ended									6 Months Ended			9 Months Ended			12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2013	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summary of Adjustments to Gross Sales [Abstract]
Gross sales	$ 633,634	$ 607,307	$ 568,016	$ 397,422	$ 278,219	$ 149,300	$ 137,235	$ 126,113	$ 123,818	$ 1,175,324	$ 427,519	$ 249,930	$ 1,808,958	$ 824,941	$ 387,165	$ 2,511,693	$ 1,433,603	$ 528,574
Less adjustments for:
Chargebacks and rebates	(331,771)	(363,008)	(293,181)	(244,288)	(132,854)	(51,873)	(49,373)	(42,966)	(43,763)	(656,189)	(184,727)	(86,729)	(987,960)	(429,014)	(136,102)	(1,361,030)	(775,964)	(183,403)
Product returns	(7,683)	(5,896)	(5,574)	(8,958)	(88)	(886)	(719)	(482)	(1,231)	(11,470)	(974)	(1,713)	(19,154)	(9,932)	(2,432)	(34,272)	(20,993)	(5,001)
Discounts and allowances	(11,744)	(11,622)	(14,044)	(8,933)	(5,462)	(2,435)	(2,228)	(1,947)	(1,975)	(25,666)	(7,897)	(3,922)	(37,410)	(16,830)	(6,150)	(50,385)	(30,782)	(8,464)
Administrative fees	(23,598)	(3,786)	(26,123)	(6,435)	(3,354)	(2,152)	(2,035)	(2,358)	(1,963)	(29,910)	(5,506)	(4,320)	(53,508)	(11,942)	(6,355)	(71,727)	(44,558)	(9,471)
Advertising, promotions, and other	(2,037)	(2,075)	(1,716)	(1,110)	(2,589)	(1,332)	(988)	(1,348)	(1,032)	(3,791)	(3,921)	(2,380)	(5,827)	(5,031)	(3,368)	(9,203)	(6,258)	(4,524)
Revenues, net	$ 256,801	$ 220,920	$ 227,378	$ 127,698	$ 133,872	$ 90,622	$ 81,892	$ 77,012	$ 73,854	$ 448,298	$ 224,494	$ 150,866	$ 705,099	$ 352,192	$ 232,758	$ 985,076	$ 555,048	$ 317,711