Supplementary Information - Summary of Property and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 95,697	$ 89,601
Less: accumulated depreciation and amortization	56,986	53,269
Property and equipment, net	38,711	36,332
Land [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	9,896	10,067
Building and Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	15,722	15,630
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	44,182	41,451
Furniture Equipment and Other [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	13,463	10,136
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	9,870	9,652
Right-of-Use Assets Under Finance Leases [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 2,564	$ 2,665