Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Revenue	$ 277,455	$ 269,998
Operating expenses	199,827	215,496
Gross margin	77,628	54,502
Corporate general and administrative expenses	10,489	11,680
Operating income	67,139	42,822
Other (expense) income:
Interest expense	(1,119)	(1,401)
Gain on sale of operations, net	95	497
Other (expense) income, net	(15,800)	9,260
Total other (expense) income, net	(16,824)	8,356
Income from continuing operations before income tax expense	50,315	51,178
Income tax expense	13,453	13,613
Income from continuing operations	36,862	37,565
Loss from discontinued operations, net of tax	(14)	(96)
Net income	$ 36,848	$ 37,469
Earnings per share - basic	$ 0.68	$ 0.69
Earnings per share - diluted	$ 0.66	$ 0.67
Basic weighted average shares outstanding	54,571	54,287
Diluted weighted average shares outstanding	55,945	55,915
Comprehensive income:
Net income	$ 36,848	$ 37,469
Other comprehensive (loss) income, net of tax	(1,252)	81
Comprehensive income	$ 35,596	$ 37,550