Goodwill and Other Intangible Assets, Net - Changes in Carrying Amount of Goodwill by Operating Segment (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 447,685	$ 435,231
Additions	39,799	14,008
Divestitures		(1,554)
Goodwill	487,484	447,685
Financial Services [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	267,485	268,630
Additions	3,845	409
Divestitures		(1,554)
Goodwill	271,330	267,485
Benefits and Insurance Services [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	178,534	164,935
Additions	35,954	13,599
Goodwill	214,488	178,534
National Practices [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	1,666	1,666
Goodwill	$ 1,666	$ 1,666

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=64834752&loc=SL49117168-202975

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