Senior Convertible Notes - Schedule of Interest Activity (Details) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended		12 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Interest Expense Debt [Roll Forward]
Interest payable on Senior Convertible Debenture, beginning of period		$ 1,988					$ 1,988
Interest paid on Senior Convertible Debentures							(2,969)		$ (7,416)
Interest payable on Senior Convertible Debenture, end of period	$ 990		$ 1,988				990		1,988
Convertible Senior Notes Due 2019
Interest Expense Debt [Roll Forward]
Interest payable on Senior Convertible Debenture, beginning of period	2,474	2,000	4,969	$ 2,222	$ 6,250	$ 2,500	2,000	$ 2,500	2,500
Accrued interest expense	1,485	486	2,982	2,747	3,388	3,750	4,400	7,100
Interest paid on Senior Convertible Debentures	(2,969)		(5,963)		(7,416)
Interest payable on Senior Convertible Debenture, end of period	$ 990	$ 2,474	$ 2,000	$ 4,969	$ 2,222	$ 6,250	$ 990	$ 2,222	$ 2,000