Revenue Recognition (Revenue disaggregated by timing of revenue recognition) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Revenue From Contract With Customer [Abstract]
Revenues recognized over time	$ 147,565	$ 2,814,732	$ 2,617,990
Revenues recognized at point in time	309,804	305,408	301,152
Total revenues recognized under ASC 606	457,369	3,120,140	2,919,142
Revenues recognized under ASC 840	3,182,902	406,070	353,924
Revenues recognized under ASC 944	200,768	131,563	217,575
Revenues recognized under ASC 320	137,829	110,934	110,473
Total revenues	$ 3,978,868	$ 3,768,707	$ 3,601,114