CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement Of Income And Comprehensive Income [Abstract]
Revenue	$ 180,885	$ 172,229	$ 389,793	$ 373,418
Operating expenses	162,307	151,091	328,494	310,480
Gross margin	18,578	21,138	61,299	62,938
Corporate general and administrative expenses	8,306	7,649	18,565	17,633
Operating income	10,272	13,489	42,734	45,305
Other income (expense):
Interest expense	(3,577)	(4,145)	(7,010)	(8,201)
Gain on sale of operations, net	68	48	76	66
Other income, net	3,936	515	5,911	2,243
Total other income (expense), net	427	(3,582)	(1,023)	(5,892)
Income from continuing operations before income tax expense	10,699	9,907	41,711	39,413
Income tax expense	4,459	4,287	17,489	16,672
Income from continuing operations after income tax expense	6,240	5,620	24,222	22,741
(Loss) income from discontinued operations, net of tax	(106)	1,622	(325)	2,781
(Loss) gain on disposal of discontinued operations, net of tax	(27)	1,905	(501)	1,928
Net income	6,107	9,147	23,396	27,450
Basic:
Continuing operations	$ 0.13	$ 0.11	$ 0.50	$ 0.46
Discontinued operations		$ 0.07	$ (0.02)	$ 0.09
Net income	$ 0.13	$ 0.18	$ 0.48	$ 0.55
Diluted:
Continuing operations	$ 0.12	$ 0.11	$ 0.46	$ 0.46
Discontinued operations		$ 0.07	$ (0.01)	$ 0.09
Net income	$ 0.12	$ 0.18	$ 0.45	$ 0.55
Basic weighted average shares outstanding	48,273	49,639	48,228	49,535
Diluted weighted average shares outstanding	52,052	49,929	52,352	49,891
Comprehensive Income:
Net income	6,107	9,147	23,396	27,450
Other comprehensive income (loss), net of tax	88	(155)	97	(63)
Comprehensive income	$ 6,195	$ 8,992	$ 23,493	$ 27,387