Convertible Senior Notes - Recognized Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Total	$ 50,882	$ 6,797	$ 0
Convertible Debt [Member]
Debt Instrument [Line Items]
Contractual interest expense based on 0.50% per annum	6,631	881
Amortization of debt discount and issuance costs	45,559	5,916
Total	$ 52,190	$ 6,797
Effective interest rate of the liability component	4.70%	4.70%