Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment	$ 240,948	$ 227,056
Less accumulated depreciation and amortization	134,650	120,580
Property and equipment, net	106,298	106,476
Office Building
Property, Plant and Equipment [Line Items]
Property and equipment	57,452	54,125
Computer Equipment and Software
Property, Plant and Equipment [Line Items]
Property and equipment	58,012	55,614
Furniture, Fixtures And Other Equipment
Property, Plant and Equipment [Line Items]
Property and equipment	77,966	72,264
Vehicles
Property, Plant and Equipment [Line Items]
Property and equipment	2,110	2,058
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment	6,725	7,536
Leasehold Land
Property, Plant and Equipment [Line Items]
Property and equipment	4,929	4,680
Residential Property
Property, Plant and Equipment [Line Items]
Property and equipment	1,700	1,602
Capital Advances / Work In Progress
Property, Plant and Equipment [Line Items]
Property and equipment	$ 32,054	$ 29,177