Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 336,230	$ 345,558	$ 338,861	$ 326,738	$ 330,377	$ 326,584	$ 329,535	$ 317,441	$ 1,347,387	$ 1,303,937	$ 1,253,646
Gross profit	98,025	102,811	101,026	93,176	97,713	96,045	100,220	92,509	395,038	386,487	375,597
Income from continuing operations	14,609	15,907	16,076	7,974	13,590	14,156	15,173	7,957	54,566	50,876	29,594
Income from discontinued operations, net of tax	(401)	(967)	58,783	18,881	2,766	2,021	1,099	1,218	76,296	7,104	3,691
Net income	$ 14,208	$ 14,940	$ 74,859	$ 26,855	$ 16,356	$ 16,177	$ 16,272	$ 9,175	$ 130,862	$ 57,980	$ 33,285
Earnings per share – basic, continuing operations (in dollars per share)	$ 0.68	$ 0.70	$ 0.67	$ 0.33	$ 0.55	$ 0.57	$ 0.61	$ 0.32	$ 2.35	$ 2.05	$ 1.17
Earnings per share – diluted, continuing operations (in dollars per share)	0.66	0.68	0.66	0.32	0.54	0.56	0.60	0.32	2.29	2.02	1.16
Earnings per share – basic (in dollars per share)	0.66	0.66	3.13	1.10	0.66	0.65	0.66	0.37	5.64	2.34	1.32
Earnings per share – diluted (in dollars per share)	$ 0.64	$ 0.64	$ 3.06	$ 1.07	$ 0.65	$ 0.64	$ 0.65	$ 0.37	$ 5.50	$ 2.30	$ 1.30