Condensed Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Comprehensive income (loss) (pretax):
Net earnings	$ 59,870	$ 2,129	$ 359,467	$ 289,329
Comprehensive income (loss) (tax effect):
Net earnings	(23,024)	(1,401)	(132,632)	(109,367)
Comprehensive income (loss) (net of tax):
Net earnings	36,846	728	226,835	179,962
Other comprehensive income (loss):
Foreign currency translation (pretax)	(1,068)	1,578	462	(4,179)
Foreign currency translation (tax effect)	0	0	0	0
Foreign currency translation (net of tax)	(1,068)	1,578	462	(4,179)
Unrealized gain (loss) on investments (pretax)	18,368	14,079	30,914	7,328
Unrealized gain (loss) on investments (tax effect)	(6,574)	(4,901)	(10,923)	(2,159)
Unrealized gain (loss) on investments (net of tax)	11,794	9,178	19,991	5,169
Change in fair value of cash flow hedges (pretax)	4,248	2,977	4,501	(13,133)
Change in fair value of cash flow hedges (tax effect)	(1,614)	(1,131)	(1,710)	4,991
Change in fair value of cash flow hedges (net of tax)	2,634	1,846	2,791	(8,142)
Total comprehensive income (loss) (pretax)	81,418	20,763	395,344	279,345
Total comprehensive income (loss) (tax effect)	(31,212)	(7,433)	(145,265)	(106,535)
Total comprehensive income (loss) (net of tax)	$ 50,206	$ 13,330	$ 250,079	$ 172,810