Segment Disclosures - Summary of Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenue	$ 266,090	$ 241,459
Operating expenses	204,750	192,766
Gross margin	61,340	48,693
Corporate general and administrative expenses	10,028	8,768
Operating income	51,312	39,925
Other (expense) income:
Interest expense	(1,780)	(1,517)
Gain on sale of operations, net	663	22
Other (expense) income, net	(1,229)	2,737
Total other (expense) income, net	(2,346)	1,242
Income from continuing operations before income tax expense	48,966	41,167
Financial Services [Member]
Segment Reporting Information [Line Items]
Revenue	180,603
Benefits and Insurance Services [Member]
Segment Reporting Information [Line Items]
Revenue	77,330
National Practices [Member]
Segment Reporting Information [Line Items]
Revenue	8,157
Operating Segments [Member] | Financial Services [Member]
Segment Reporting Information [Line Items]
Revenue	180,603	158,633
Operating expenses	133,033	119,389
Gross margin	47,570	39,244
Operating income	47,570	39,244
Other (expense) income:
Other (expense) income, net	265	15
Total other (expense) income, net	265	15
Income from continuing operations before income tax expense	47,835	39,259
Operating Segments [Member] | Benefits and Insurance Services [Member]
Segment Reporting Information [Line Items]
Revenue	77,330	75,164
Operating expenses	61,133	60,142
Gross margin	16,197	15,022
Operating income	16,197	15,022
Other (expense) income:
Interest expense	(75)	(11)
Gain on sale of operations, net	663
Other (expense) income, net	193	96
Total other (expense) income, net	781	85
Income from continuing operations before income tax expense	16,978	15,107
Operating Segments [Member] | National Practices [Member]
Segment Reporting Information [Line Items]
Revenue	8,157	7,662
Operating expenses	7,275	7,007
Gross margin	882	655
Operating income	882	655
Other (expense) income:
Income from continuing operations before income tax expense	882	655
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating expenses	3,309	6,228
Gross margin	(3,309)	(6,228)
Corporate general and administrative expenses	10,028	8,768
Operating income	(13,337)	(14,996)
Other (expense) income:
Interest expense	(1,705)	(1,506)
Gain on sale of operations, net		22
Other (expense) income, net	(1,687)	2,626
Total other (expense) income, net	(3,392)	1,142
Income from continuing operations before income tax expense	$ (16,729)	$ (13,854)