Property and Equipment - Property and Equipment, Net (Detail) - USD ($)	Mar. 31, 2018	Mar. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 230,788,000	$ 206,780,000
Less: accumulated depreciation and amortization	(161,432,000)	(143,738,000)
Property and equipment, net	69,356,000	63,042,000
Computer Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	142,754,000	130,641,000
Office Equipment And Computers [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	67,730,000	65,246,000
Land and Building [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	5,843,000	0
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 14,461,000	$ 10,893,000