Convertible Notes - Schedule of Interest Expense (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended		3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Senior Notes Due 2019 [Member]	Jun. 30, 2014 Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Contractual interest expense			$ 1,198	$ 1,198
Amortization of debt issuance costs			611	611
Amortization of debt discount	5,780	0	5,169	5,169
Debt Instrument, Interest Expense, Total			$ 6,978	$ 6,978