Revenue Recognition (Revenue disaggregated by timing of revenue recognition) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Revenue From Contract With Customer [Abstract]
Revenues recognized over time	$ 2,814,732	$ 2,617,990	$ 2,494,060
Revenues recognized at point in time	305,408	301,152	291,886
Total revenues recognized under ASC 606	3,120,140	2,919,142	2,785,946
Revenues recognized under ASC 840	406,070	353,924	311,403
Revenues recognized under ASC 944	131,563	217,575	222,142
Revenues recognized under ASC 320	110,934	110,473	102,276
Total revenues	$ 3,768,707	$ 3,601,114	$ 3,421,767