Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Comprehensive income (loss) (pretax):
Pretax earnings (loss)	$ 215,660	$ 197,358	$ 384,857	$ 396,044
Comprehensive income (loss) (tax effect):
Net earnings	(52,118)	(72,719)	(93,466)	(145,198)
Comprehensive income (loss) (net of tax):
Net earnings	163,542	124,639	291,391	250,846
Other comprehensive income (loss):
Foreign currency translation (pretax)	1,113	12,767	(980)	21,034
Foreign currency translation (tax effect)
Foreign currency translation (net of tax)	1,113	12,767	(980)	21,034
Unrealized gain (loss) on investments (pretax)	(22,280)	15,473	(72,498)	26,104
Unrealized gain (loss) on investments (tax effect)	4,679	(5,416)	15,225	(9,136)
Unrealized gain (loss) on investments (net of tax)	(17,601)	10,057	(57,273)	16,968
Change in fair value of cash flow hedges (pretax)	286	1,194	846	2,744
Change in fair value of cash flow hedges (tax effect)	(70)	(454)	(208)	(1,044)
Change in fair value of cash flow hedges (net of tax)	216	740	638	1,700
Total comprehensive income (loss) (pretax)	194,779	226,792	312,225	445,926
Total comprehensive income (loss) (tax effect)	(47,509)	(78,589)	(78,449)	(155,378)
Total comprehensive income (loss) (net of tax)	$ 147,270	$ 148,203	$ 233,776	$ 290,548