Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Revenue	$ 1,849,441	$ 1,663,112	$ 5,494,194	$ 4,923,957
Operating costs and expenses:
Cost of revenue	813,500	750,680	2,498,096	2,285,062
Billable expenses	600,522	510,047	1,691,543	1,465,831
General and administrative expenses	245,719	222,673	724,121	655,410
Depreciation and amortization	20,655	17,780	60,308	50,359
Total operating costs and expenses	1,680,396	1,501,180	4,974,068	4,456,662
Operating income	169,045	161,932	520,126	467,295
Interest expense	(24,231)	(22,036)	(75,281)	(67,357)
Other income (expense), net	1,909	373	5,885	(2,415)
Income before income taxes	146,723	140,269	450,730	397,523
Income tax expense	34,697	8,232	106,993	68,569
Net income	$ 112,026	$ 132,037	$ 343,737	$ 328,954
Earnings per common share (Note 4):
Basic (in dollars per share)	$ 0.79	$ 0.92	$ 2.44	$ 2.29
Diluted (in dollars per share)	$ 0.79	$ 0.92	$ 2.42	$ 2.27