Income Taxes - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Unrecognized tax benefits	$ 2,800,000	$ 1,300,000	$ 2,800,000	$ 1,300,000
Interest and penalties	$ 0	$ 0	$ 0	$ 22,000
Effective income tax rate (as percent)	20.70%	35.20%	20.30%	31.90%
Federal and State income tax statutory rate (as percent)			26.14%	39.23%
Excess tax benefit	$ 199,000	$ 59,000	$ 3,000,000	$ 4,600,000