Revenue Recognition (Revenue disaggregated by timing of revenue recognition) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenues [Abstract]
Total revenues	$ 1,658,108	$ 1,649,860	$ 3,206,598	$ 3,190,168
Insurance premium revenues recognized under ASC 944
Revenues [Abstract]
Total revenues	47,820	49,472	90,968	93,964
Net investment and interest income recognized under other topics
Revenues [Abstract]
Total revenues	37,794	64,738	74,919	129,330
Revenues recognized under ASC 842
Revenues [Abstract]
Total revenues	1,339,320	1,305,523	2,593,637	2,527,839
Revenues recognized under ASC 606
Revenues [Abstract]
Total revenues	233,174	230,127	447,074	439,035
Revenues recognized over time:
Revenues [Abstract]
Total revenues	125,792	118,368	225,967	209,683
Revenues recognized at a point in time:
Revenues [Abstract]
Total revenues	$ 107,382	$ 111,759	$ 221,107	$ 229,352