Income Taxes - Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
U.S. statutory income tax rate	21.00%	35.00%	35.00%
State tax, net of U.S. federal tax benefit	5.70%	5.00%	2.40%
Non-U.S. income taxes	0.10%	(0.10%)	0.30%
Nondeductible operating expenses	3.10%	0.80%	0.30%
Research and development credit	(3.10%)	(1.50%)	(1.00%)
Change in deferred tax measurement rate	0.10%	(15.30%)	(0.10%)
Change in uncertain tax positions	0.80%	0.80%	(5.10%)
Excess tax benefits from stock plans	(0.70%)	(2.10%)	0.00%
Valuation allowance	1.80%	0.10%	0.20%
Other	(0.70%)	(0.10%)	(0.10%)
Effective income tax rate for continuing operations	28.10%	22.60%	31.90%
Valuation allowance	$ 1,247	$ 914
Net Operating Loss Carryforward | Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Valuation allowance	200
Loss and Other Credit Carryforward | Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Valuation allowance	900
Loss and Other Credit Carryforward | Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 300
Accounting Standards Update 2018-05
Operating Loss Carryforwards [Line Items]
Change in deferred tax measurement rate	1.00%
Tax Cuts And Jobs Act Of 2017, incomplete accounting, change in tax rate, deferred tax asset, provisional income tax expense	$ (100)