Income Taxes (Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
U.S. federal income tax rate	35.00%	35.00%	35.00%
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
United States federal tax expense (benefit) at statutory rate	$ (28,938)	$ (24,687)	$ (18,930)
State taxes, net of United States federal tax expense (benefit)	(1,240)	(1,083)	(841)
Change in valuation allowance	27,821	27,759	25,046
Non-deductible stock compensation	218	270	415
Impact of non-U.S. jurisdictional tax rate difference	648	529	487
Research and development tax credit	(243)	(325)	(1,632)
Increase (reversal) of unrecognized tax benefits	(1,269)	(901)	671
Non-U.S. withholding tax	141	393	1,805
Other	2,028	(675)	(2,118)
Total income tax expense (benefit)	$ (834)	$ 1,280	$ 4,903