Debt Obligations (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jul. 15, 2016	Jul. 25, 2011	Jul. 30, 2008
Debt Instrument [Line Items]
Investment Warrants, Exercise Price	$ 23,130	$ 19,820
Document Period End Date		Dec. 31, 2016
Debt Instrument, Face Amount		$ 0	$ 60,000		$ 60,000	$ 60,000
Class of Warrant or Right, Number of Securities Called by Warrants or Rights		386					4,634
Debt Instrument, Interest Rate, Stated Percentage						3.75%
Debt Instrument, Unamortized Discount		$ 0	1,893
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net		0	261
Convertible Debt, Current		0	57,846
Convertible Debt, Noncurrent			57,846
Contractual Interest Coupon		1,186	2,250	$ 2,250
Amortization of Debt Discount (Premium)		1,893	3,334	3,022
Amortization of Financing Costs		261	432	363
Interest Expense, Debt		$ 3,340	$ 6,016	$ 5,635
Warrant Strike Price		$ 17.00
Redemption of stock warrants	102	4,248
Stock Issued During Period, Value, Conversion of Convertible Securities		$ 10,525
Payments for Repurchase of Warrants		$ 9,500
Common Stock [Member]
Debt Instrument [Line Items]
Redemption of stock warrants		80