Convertible Senior Notes - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Debt Disclosure [Abstract]
Amortization of debt discount	$ 459	$ 442	$ 914	$ 630
Amortization of debt issuance costs	4,838	4,671	9,634	6,661
Capitalization of interest expense	(619)	(597)	(1,294)	(834)
Interest expense	$ 4,678	$ 4,516	$ 9,254	$ 6,457