Income Taxes - Schedule of Income before Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income before provision for income taxes
U.S. income before provision for income taxes	$ 149,338	$ 132,882	$ 101,007
Foreign income before provision for income taxes	11,062	10,521	11,737
Income before provision for income taxes	160,400	143,403	112,744
Current taxes:
U.S. federal	58,082	42,056	32,065
State and local	8,155	7,423	6,442
Non-U.S.	1,991	2,014	2,508
Total	68,228	51,493	41,015
Deferred taxes:
U.S. federal	(428)	(743)	6,334
State and local	(412)	(86)	1,273
Non-U.S.	526	(71)	(215)
Deferred income taxes	(314)	(900)	7,392
Provision for income taxes	$ 67,914	$ 50,593	$ 48,407