Convertible Notes - Schedule of Interest Expense (Details) - Senior Notes Due 2019 [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Debt Instrument [Line Items]
Contractual interest expense	$ 1,797	$ 1,797	$ 5,391	$ 5,391
Amortization of debt issuance costs	1,021	997	3,045	2,971
Amortization of debt discount	8,284	8,039	24,667	23,939
Debt Instrument, Interest Expense, Total	$ 11,102	$ 10,833	$ 33,103	$ 32,301