Revenue Recognition (Revenue disaggregated by timing of revenue recognition) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue From Contract With Customer [Abstract]
Revenues Recognized Over Time	$ 835,307	$ 786,065	$ 1,593,043	$ 1,492,137
Revenues recognized at a point in time	84,719	84,721	174,909	173,859
Total revenues recognized under ASC 606	920,026	870,786	1,767,952	1,665,996
Revenues recognized under ASC 840	102,831	89,464	198,688	172,916
Revenues recognized under ASC 944	53,423	55,967	104,612	108,013
Revenues recognized under ASC 320	28,227	26,469	52,832	53,686
Total revenues	$ 1,104,507	$ 1,042,686	$ 2,124,084	$ 2,000,611