Convertible Senior Notes - Schedule of Interest Expense (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Debt Disclosure [Abstract]
Amortization of debt discount	$ 449		$ 1,079
Amortization of debt issuance costs	4,712		11,373
Capitalization of interest expense	(679)		(1,513)
Interest expense	$ 4,482	$ 0	$ 10,939	$ 0