Convertible Senior Notes - Schedule of Interest Expense (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Debt Disclosure [Abstract]
Amortization of debt discount	$ 188
Amortization of debt issuance costs	1,990
Capitalization of interest expense	(237)
Interest expense	$ 1,941	$ 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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