Debt Obligations - (Details) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2011	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	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		6,775		6,775		8,249
Convertible senior notes		53,225		53,225		51,751
Contractual Interest Coupon		563	562	1,125	1,124
Amortization of Debt Discount (Premium)		739	670	1,474	1,337
Amortization of Financing Costs		87	73	174	145
Interest Expense, Debt		$ 1,389	$ 1,305	$ 2,773	$ 2,606