Debt Obligations - (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	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	9,653		9,653		10,990
Convertible senior notes	50,347		50,347		49,010
Contractual Interest Coupon	562	562	1,124	1,125
Amortization of Debt Discount (Premium)	670	608	1,337	1,213
Amortization of Financing Costs	73	60	145	119
Interest Expense, Debt	$ 1,305	$ 1,230	$ 2,606	$ 2,457