Condensed Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Comprehensive income (loss) (pretax):
Net earnings	$ 325,636	$ 289,314	$ 100,190
Comprehensive income (loss) (tax effect):
Net earnings	(120,269)	(105,739)	(34,567)
Comprehensive income (loss) (net of tax):
Net earnings	205,367	183,575	65,623
Other comprehensive income (loss):
Foreign currency translation (pretax)	(2,854)	3,114	14,471
Foreign currency translation (tax effect)	0	0	0
Foreign currency translation (net of tax)	(2,854)	3,114	14,471
Unrealized gain (loss) on investments (pretax)	15,094	7,468	20,546
Unrealized gain (loss) on investments (tax effect)	(5,089)	(2,538)	(7,292)
Unrealized gain (loss) on investments (net of tax)	10,005	4,930	13,254
Change in fair value of cash flow hedges (pretax)	(9,179)	2,411	23,352
Change in fair value of cash flow hedges (tax effect)	3,488	(916)	(8,874)
Change in fair value of cash flow hedges (net of tax)	(5,691)	1,495	14,478
Postretirement benefit obligation gain (loss) (pretax)	(692)	324	(661)
Postretirement benefit obligation gain (loss) (tax effect)	263	(123)	251
Postretirement benefit obligation gain (loss) (net of tax)	(429)	201	(410)
Total comprehensive income (loss) (pretax)	328,005	302,631	157,898
Total comprehensive income (loss) (tax effect)	(121,607)	(109,316)	(50,482)
Total comprehensive income (loss) (net of tax)	$ 206,398	$ 193,315	$ 107,416