Revenue Recognition (Revenue disaggregated by timing of revenue recognition) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue From Contract With Customer [Abstract]
Revenues Recognized Over Time	$ 48,986	$ 835,307	$ 88,065	$ 1,593,043
Revenues recognized at a point in time	86,265	84,719	177,436	174,909
Total revenues recognized under ASC 606	135,251	920,026	265,501	1,767,952
Revenues recognized under ASC 840	929,790	102,831	1,794,994	198,688
Revenues recognized under ASC 944	52,075	53,423	100,121	104,612
Revenues recognized under ASC 320	33,098	28,227	68,847	52,832
Total revenues	$ 1,150,214	$ 1,104,507	$ 2,229,463	$ 2,124,084