Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Net service revenues	$ 327,699	$ 341,575	$ 337,353	$ 312,611	$ 318,739	$ 313,810	$ 302,758	$ 282,024	$ 1,319,238	$ 1,217,331	$ 1,073,728
Gross profit	103,515	109,821	106,038	94,740	98,378	98,291	94,386	83,526	414,114	374,581	344,376
Income from continuing operations, net of income taxes	11,901	13,545	11,593	5,785	9,061	7,995	7,953	4,389	42,824	29,398	5,294
Income (loss) from discontinued operations, net of income taxes	0	0	0	0	(116)	57,023	2,750	1,860	0	61,517	5,493
Net income	$ 11,901	$ 13,545	$ 11,593	$ 5,785	$ 8,945	$ 65,018	$ 10,703	$ 6,249	$ 42,824	$ 90,915	$ 10,787
Earnings per share – basic (in dollars per share)	$ 0.43	$ 0.49	$ 0.41	$ 0.20	$ 0.30	$ 2.07	$ 0.33	$ 0.19	$ 1.53	$ 2.89	$ 0.32
Earnings per share – diluted (in dollars per share)	$ 0.43	$ 0.48	$ 0.41	$ 0.20	$ 0.30	$ 2.06	$ 0.33	$ 0.19	$ 1.52	$ 2.87	$ 0.32