Convertible Notes - Schedule of Interest Expense (Details) - Senior Notes Due 2019 [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Debt Instrument [Line Items]
Contractual interest expense	$ 1,797	$ 1,797	$ 5,391	$ 2,995
Amortization of debt issuance costs	997	922	2,971	1,533
Amortization of debt discount	8,039	7,802	23,939	12,971
Debt Instrument, Interest Expense, Total	$ 10,833	$ 10,521	$ 32,301	$ 17,499