Convertible Senior Notes - Schedule of Interest Expense (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Debt Disclosure [Abstract]
Amortization of debt discount	$ 442		$ 630
Amortization of debt issuance costs	4,671		6,661
Capitalization of interest expense	(597)		(834)
Interest expense	$ 4,516	$ 0	$ 6,457	$ 0

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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