Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets
Net operating loss carryforwards	$ 1,325	$ 11,250
Research and development credit carryforwards	20,182	16,901
Foreign tax credit carryforwards	2,586	2,209
Accrued liabilities	1,109	4,180
Deferred revenues	4,843	4,200
Intangible assets	327	0
Stock-based compensation	5,942	6,975
Other	158	174
Gross deferred tax assets	49,659	45,889
Valuation allowance	(10,094)	(9,100)
Net deferred tax assets	39,565	36,789
Deferred tax liabilities
Fixed assets	(8,097)	(8,160)
Deferred Tax Liabilities, Right-of-Use Assets	(10,496)	0
Deferred Tax Liabilities, Deferred Commission	(2,142)	(1,458)
Intangible assets	0	(784)
Total deferred tax liabilities	(20,735)	(10,402)
Net deferred tax assets	18,830	26,387
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Deferred Rent	$ 13,187	$ 0