Income Taxes (Net Deferred Tax Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets [Abstract]
United States federal net operating loss carryforwards	$ 62,983	$ 59,457
Deferred expenses	660	926
Research and development tax credit carryforwards	24,523	24,499
Net unrealized loss on investments	62	62
Accrued loss on excess office facilities	291	489
Stock-based compensation	2,603	2,738
State net operating loss carryforwards	11,971	13,746
Foreign net operating loss carryforwards	31,254	32,759
Deferred revenue	67	108
Equipment, software, and leasehold improvements	2,642	3,119
Intangibles	13	2
Net unrealized gains and basis differences on investments	1,193	1,188
Other	486	183
Gross deferred tax assets	138,748	139,276
Less valuation allowance	137,246	137,117
Gross deferred tax assets, net of valuation allowance	1,502	2,159
Deferred tax liabilities:
Other intangible assets	(155)	(62)
Undistributed foreign earnings	1,001	0
Other	(479)	(814)
Prepaid expenses	(184)	(254)
Gross deferred tax liabilities	(1,819)	(1,130)
Net deferred tax assets (liabilities)	$ (317)
Net deferred tax assets (liabilities)		$ 1,029