Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Revenue	$ 224,238	$ 213,866
Operating expenses	178,117	170,864
Gross margin	46,121	43,002
Corporate general and administrative expenses	10,245	9,865
Operating income	35,876	33,137
Other income (expense):
Interest expense	(1,526)	(2,977)
Gain on sale of operations, net	101	56
Other income, net	2,147	2,859
Total other income (expense), net	722	(62)
Income from continuing operations before income tax expense	36,598	33,075
Income tax expense	14,800	13,572
Income from continuing operations	21,798	19,503
Loss from operations of discontinued operations, net of tax	(30)	(335)
Net income	$ 21,768	$ 19,168
Basic:
Continuing operations	$ 0.42	$ 0.41
Discontinued operations		(0.01)
Net income	0.42	0.40
Diluted:
Continuing operations	0.41	0.38
Discontinued operations		(0.01)
Net income	$ 0.41	$ 0.37
Basic weighted average shares outstanding	51,572	48,146
Diluted weighted average shares outstanding	52,745	51,385
Comprehensive Income:
Net income	$ 21,768	$ 19,168
Other comprehensive (loss) income, net of tax	(311)	138
Comprehensive income	$ 21,457	$ 19,306