Senior Convertible Notes - Schedule of Activity and Balances Associated with the Notes and Related Deferred Transaction Costs (Details) - USD ($) $ in Thousands				1 Months Ended	3 Months Ended
	Mar. 01, 2017	Feb. 28, 2017	Mar. 18, 2016	Nov. 30, 2016	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
Convertible Notes And Deferred Transaction Costs[Roll forward]
Less: amortization					$ (608)				$ (4,153)
Conversions					(4,912)				(82,274)
Convertible Senior Notes Due 2019
Convertible Notes And Deferred Transaction Costs[Roll forward]
Notes Balance, beginning of period					23,514	$ 79,182	$ 79,182	$ 79,182	159,011
Deferred Debt Costs, beginning of period					849	3,112	3,364	3,617	7,770
Notes, net of Debt Costs, beginning of period					22,665	76,070	75,818	75,565	151,241
Less: amortization		$ (1,591)			(608)	(2,263)	(252)	(253)	(4,153)
Conversions	$ (4,900)		$ (79,800)	$ (55,700)	(4,911)	(55,668)			(79,829)
Notes Balance, end of period					18,603	23,514	79,182	79,182	79,182
Deferred Debt Costs, end of period					1,832	849	3,112	3,364	3,617
Notes, net of Debt Costs, end of period					$ 16,771	$ 22,665	$ 76,070	$ 75,818	$ 75,565