Debt Obligations - (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2011	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Jul. 25, 2011
Debt Obligations [Abstract]
Convertible Debt		$ 60,000		$ 60,000		$ 60,000	$ 60,000
Debt Instrument, Interest Rate, Stated Percentage							3.75%
Convertible Preferred Stock, Shares Issued upon Conversion							77.241
Note increment for which conversion amount of Common Stock based							$ 1
Debt Instrument, Convertible, Conversion Price							$ 12.95
Class of Warrant or Right, Exercise Price of Warrants or Rights							$ 17.00
Proceeds from Convertible Debt	$ 50,249
Debt Instrument, Unamortized Discount		3,601		3,601		5,227
Convertible senior notes		56,399		56,399		$ 54,773
Contractual Interest Coupon		563	$ 563	1,125	$ 1,125
Amortization of Debt Discount (Premium)		815	739	1,626	1,474
Amortization of Financing Costs		104	87	207	174
Interest Expense, Debt		$ 1,482	$ 1,389	$ 2,958	$ 2,773