Debt - Schedule of Activity and Balances Associated with the Notes and Related Deferred Transaction Costs (Details) - USD ($) $ in Thousands			1 Months Ended		3 Months Ended			9 Months Ended
	Feb. 28, 2017	Mar. 18, 2016	Mar. 31, 2017	Nov. 30, 2016	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2016
Convertible Notes And Deferred Transaction Costs[Roll forward]
Less: amortization of deferred financing cost								$ (1,014)	$ (4,658)
Conversions								(4,912)	$ (82,274)
Convertible Senior Notes Due 2019
Convertible Notes And Deferred Transaction Costs[Roll forward]
Notes Balance, beginning of period					$ 18,603	$ 18,603	$ 23,514	23,514
Deferred Debt Costs, beginning of period					1,655	1,832	849	849
Notes, net of Deferred Debt Costs, beginning of period					16,948	16,771	22,665	22,665
Less: amortization of deferred financing cost					(59)	(59)	(608)
Conversions		$ (79,800)	$ (4,900)	$ (55,700)			(4,911)
Notes Balance, end of period			18,603		18,603	18,603	18,603	18,603
Deferred Debt Costs, end of period			1,832		1,478	1,655	1,832	1,478
Less: amortization of debt modification cost	$ (1,591)				(118)	(118)
Notes, net of Deferred Debt Costs, end of period			$ 16,771		$ 17,125	$ 16,948	$ 16,771	$ 17,125