Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets
Net operating loss carryforwards	$ 1,472	$ 1,936
Research and development credit carryforwards	3,334	6,508
Accrued liabilities	681	614
Deferred revenues	5,018	3,838
Deferred rent	74	142
Intangible assets	409	246
Stock-based compensation	12,513	8,301
Other	1,225	1,396
Gross deferred tax assets	24,726	22,981
Valuation allowance	(3,688)	(3,303)
Net deferred tax assets	21,038	19,678
Deferred tax liabilities
Fixed assets	(4,448)	(3,599)
Intangible assets	0	0
Total deferred tax liabilities	(4,448)	(3,599)
Net deferred tax assets	$ 16,590	$ 16,079