Senior Convertible Notes - Schedule of Activity and Balances Associated with the Notes and Related Deferred Transaction Costs (Details) - USD ($) $ in Thousands		1 Months Ended	2 Months Ended	3 Months Ended								12 Months Ended
	Mar. 18, 2016	Nov. 30, 2016	Dec. 31, 2014	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Convertible Notes And Deferred Transaction Costs[Roll forward]
Less: amortization												$ (6,921)	$ (4,566)	$ (411)
Conversions												(137,941)	(40,989)	0
Notes, net of Debt Costs, end of period				$ 28,665								28,665
Convertible Senior Notes Due 2019
Convertible Notes And Deferred Transaction Costs[Roll forward]
Notes Balance, beginning of period			$ 200,000	79,182	$ 79,182	$ 79,182	$ 159,011	$ 159,011	$ 177,787	$ 200,000	$ 200,000	159,011	200,000
Deferred Debt Costs, beginning of period			12,747	3,112	3,364	3,617	7,770	8,276	9,820	11,719	12,336	7,770	12,336
Notes, net of Debt Costs, beginning of period			187,253	76,070	75,818	75,565	151,241	150,735	167,967	188,281	187,664	151,241	187,664
Less: amortization	$ (3,600)	$ (2,000)	(411)	(2,263)	(252)	(253)	(4,153)	(506)	(1,544)	(1,899)	(617)	(6,900)	(4,600)
Conversions	$ (79,800)	$ (55,700)		(55,668)			(79,829)		(18,776)	(22,213)
Notes Balance, end of period			200,000	23,514	79,182	79,182	79,182	159,011	159,011	177,787	200,000	23,514	159,011	200,000
Deferred Debt Costs, end of period			12,336	849	3,112	3,364	3,617	7,770	8,276	9,820	11,719	849	7,770	12,336
Notes, net of Debt Costs, end of period			$ 187,664	$ 22,665	$ 76,070	$ 75,818	$ 75,565	$ 151,241	$ 150,735	$ 167,967	$ 188,281	$ 22,665	$ 151,241	$ 187,664