Consolidated Quarterly Financial Data-Unaudited (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended									12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Quarterly Financial Data-Unaudited
U.S. product sales, net	$ 46,648	$ 22,547	$ 22,225	$ 17,375	$ 18,981	$ 19,347	$ 17,456	$ 15,578		$ 108,795	$ 71,362	$ 58,287
License fee and other collaboration revenues	3,462	2,182	2,122	3,120	2,329	1,998	2,055	2,003		10,886	8,385	26,475
Other product sales and royalties	3,143	765	455	340	401	271	138	299		4,703	1,109	616
Total revenues	53,253	25,494	24,802	20,835	21,711	21,616	19,649	17,880		124,384	80,856	85,378
Cost of product sales	11,758	2,968	2,743	2,837	3,326	2,547	3,145	2,942		20,306	11,960	14,220
Gross margin	41,495	22,526	22,059	17,998	18,385	19,069	16,504	14,938
Operating expenses	44,869	18,233	20,824	23,989	22,380	19,464	19,260	19,409
Interest expense	(7,041)	(3,129)	(3,051)	(1,476)						(14,697)
Interest and dividend income, net	166	291	253	265	278	246	256	271		975	1,051	1,286
Gains on assets held for sale	1		2	100	59		566	299
Gains on investments, net	97	3	14		4	4	26	6		114	40	(1,466)
Net income (loss) before income taxes	(10,151)	1,458	(1,547)	(7,102)						(17,342)	(9,602)	(17,604)
Income tax benefit	153,159									153,159		854
Net income (loss)	143,008	1,458	(1,547)	(7,102)	(3,654)	(145)	(1,908)	(3,895)		135,817	(9,602)	(16,750)
Net income (loss) per share - basic (in dollars per share)	$ 5.98	$ 0.07	$ (0.07)	$ (0.33)						$ 6.06	$ (0.44)	$ (0.78)
Net income (loss) per share - diluted (in dollars per share)	$ 4.67	$ 0.07	$ (0.07)	$ (0.33)						$ 5.45	$ (0.44)	$ (0.78)
Basic and diluted (in dollars per share)					$ (0.17)	$ (0.01)	$ (0.09)	$ (0.18)
Reduction in estimated Medicaid rebate reserve related to Feraheme sales						$ 23,200			$ 23,200		$ (568)	$ (621)