Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Revenue	$ 236,943	$ 235,498	$ 514,398	$ 505,496
Operating expenses	209,016	198,148	408,843	413,644
Gross margin	27,927	37,350	105,555	91,852
Corporate general and administrative expenses	11,160	10,566	21,649	22,246
Operating income	16,767	26,784	83,906	69,606
Other income (expense):
Interest expense	(2,074)	(1,587)	(3,193)	(2,988)
Gain on sale of operations, net	57	50	152	547
Other income (expense), net	13,336	(3,311)	(2,464)	5,949
Total other income (expense), net	11,319	(4,848)	(5,505)	3,508
Income from continuing operations before income tax expense	28,086	21,936	78,401	73,114
Income tax expense	6,607	5,322	20,060	18,935
Income from continuing operations	21,479	16,614	58,341	54,179
Loss from discontinued operations, net of tax	(11)	(22)	(25)	(118)
Net income	$ 21,468	$ 16,592	$ 58,316	$ 54,061
Earnings per share Basic:
Continuing operations	$ 0.40	$ 0.31	$ 1.07	$ 1.00
Discontinued operations
Net income	0.40	0.31	1.07	1.00
Earnings per share Diluted:
Continuing operations	0.39	0.30	1.05	0.97
Discontinued operations
Net income	$ 0.39	$ 0.30	$ 1.05	$ 0.97
Basic weighted average shares outstanding	54,142	54,090	54,356	54,188
Diluted weighted average shares outstanding	55,116	55,495	55,515	55,701
Comprehensive income:
Net income	$ 21,468	$ 16,592	$ 58,316	$ 54,061
Other comprehensive loss, net of tax	(377)	(422)	(1,629)	(341)
Comprehensive income	$ 21,091	$ 16,170	$ 56,687	$ 53,720