Accounts Receivable, Net of Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Current assets:
Accounts receivable–billed	$ 474,822	$ 494,671
Accounts receivable–unbilled	988,634	846,372
Allowance for doubtful accounts	(3,985)	(10,679)
Accounts receivable, net of allowance	1,459,471	1,330,364
Other long-term assets:
Accounts receivable–unbilled	62,600	61,391
Total accounts receivable, net	1,522,071	1,391,755
Provision for doubtful accounts	$ (6,400)	$ 11,900	$ 700