Acquisitions (First Quarter 2017) - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) Business	Dec. 31, 2016 USD ($)
Business Acquisition, Contingent Consideration [Line Items]
Contingent consideration, current	$ 14,382	$ 16,322
Contingent consideration, non-current	18,040	17,387
Goodwill	$ 489,039	$ 487,484
Pacific Coastal Pension and Insurance Services, Inc. (Pacific Coastal) [Member]
Business Acquisition, Contingent Consideration [Line Items]
Number of businesses acquired | Business	1
Acquired entity, name	Pacific Coastal Pension and Insurance Services, Inc.
Consideration paid in cash	$ 600
Contingent consideration	1,700
Contingent consideration, current	500
Contingent consideration, non-current	1,200
Annual revenue	$ 1,400
Effective date of acquisition	Feb. 01, 2017
Goodwill	$ 1,515