CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenues	$ 1,159,368
Revenues	1,159,368	$ 1,084,385	$ 963,364
Operating expenses:
Employee compensation and benefits	737,762	692,073	636,631
Travel, meals, and entertainment	41,945	42,862	26,445
Rent	44,693	38,672	28,560
Depreciation and amortization	17,291	14,475	7,905
Information technology and communications	26,904	21,512	18,481
Professional fees	21,704	23,035	17,117
Other operating expenses	39,468	32,659	13,812
Total operating expenses	929,767	865,288	748,951
Operating income	229,601	219,097	214,413
Other (income)/expense, net	(6,046)	(5,223)	(3,423)
Income before provision for income taxes	235,647	224,320	217,836
Provision for income taxes	51,854	65,214	45,553
Net income	183,793	159,106	172,283
Other comprehensive income, net of tax:
Foreign currency translation adjustments	(12,814)	(16,338)	7,961
Comprehensive income	$ 170,979	$ 142,768	$ 180,244
Weighted average shares of common stock outstanding:
Basic (in shares)	62,152,870	62,213,414	62,494,275
Diluted (in shares)	65,725,516	65,846,132	66,324,093
Earnings per share (Note 13)
Basic (in usd per share)	$ 2.96	$ 2.56	$ 2.76
Diluted (in usd per share)	$ 2.80	$ 2.42	$ 2.60