Segment Disclosures - Summary of Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Revenue	$ 199,794	$ 187,102	$ 621,047	$ 586,010
Operating expenses	174,069	158,496	526,182	492,477
Gross margin	25,725	28,606	94,865	93,533
Corporate general & admin	8,679	8,028	27,270	24,508
Operating income	17,046	20,578	67,595	69,025
Other income (expense):
Interest expense	(1,760)	(1,840)	(5,019)	(7,665)
Gain on sale of operations, net	329	5	480	106
Other income (expense), net	2,632	(2,367)	5,482	(634)
Total other income (expense), net	1,201	(4,202)	943	(8,193)
Income from continuing operations before income tax expense	18,247	16,376	68,538	60,832
Operating Segments [Member] | Financial Services [Member]
Segment Reporting Information [Line Items]
Revenue	123,049	118,354	398,112	378,857
Operating expenses	105,615	101,597	326,099	312,560
Gross margin	17,434	16,757	72,013	66,297
Operating income	17,434	16,757	72,013	66,297
Other income (expense):
Other income (expense), net	10	93	237	193
Total other income (expense), net	10	93	237	193
Income from continuing operations before income tax expense	17,444	16,850	72,250	66,490
Operating Segments [Member] | Employee Services [Member]
Segment Reporting Information [Line Items]
Revenue	68,979	61,293	199,790	184,968
Operating expenses	57,627	50,754	167,651	153,524
Gross margin	11,352	10,539	32,139	31,444
Operating income	11,352	10,539	32,139	31,444
Other income (expense):
Interest expense	(12)	(9)	(32)	(28)
Other income (expense), net	62	173	220	371
Total other income (expense), net	50	164	188	343
Income from continuing operations before income tax expense	11,402	10,703	32,327	31,787
Operating Segments [Member] | National Practices [Member]
Segment Reporting Information [Line Items]
Revenue	7,766	7,455	23,145	22,185
Operating expenses	6,895	6,644	20,777	19,894
Gross margin	871	811	2,368	2,291
Operating income	871	811	2,368	2,291
Other income (expense):
Other income (expense), net	1	2	2	3
Total other income (expense), net	1	2	2	3
Income from continuing operations before income tax expense	872	813	2,370	2,294
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating expenses	3,932	(499)	11,655	6,499
Gross margin	(3,932)	499	(11,655)	(6,499)
Corporate general & admin	8,679	8,028	27,270	24,508
Operating income	(12,611)	(7,529)	(38,925)	(31,007)
Other income (expense):
Interest expense	(1,748)	(1,831)	(4,987)	(7,637)
Gain on sale of operations, net	329	5	480	106
Other income (expense), net	2,559	(2,635)	5,023	(1,201)
Total other income (expense), net	1,140	(4,461)	516	(8,732)
Income from continuing operations before income tax expense	$ (11,471)	$ (11,990)	$ (38,409)	$ (39,739)