Accounts and Taxes Payable and Accrued Liabilities - Accrued Liabilities (Detail) - USD ($)	Dec. 31, 2020	Mar. 31, 2020
Payables And Accruals [Abstract]
Payroll, payroll taxes and employee benefits	$ 38,254,000	$ 26,024,000
Customer deposits	54,371,000	48,991,000
Accrued professional service fees	6,443,000	5,919,000
Self-insurance accruals	3,319,000	3,248,000
Deferred revenue	22,522,000	17,645,000
Operating lease liabilities	13,653,000	13,223,000
Other	2,766,000	2,276,000
Total accrued liabilities	$ 141,328,000	$ 117,326,000