Condensed Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Comprehensive income (loss) (pretax):
Pretax earnings (loss)	$ 107,433	$ 82,366	$ 549,362	$ 478,262
Comprehensive income (loss) (tax effect):
Net earnings	(40,893)us-gaap_IncomeTaxExpenseBenefit	(30,145)us-gaap_IncomeTaxExpenseBenefit	(202,101)us-gaap_IncomeTaxExpenseBenefit	(175,082)us-gaap_IncomeTaxExpenseBenefit
Comprehensive income (loss) (net of tax):
Net earnings	66,540us-gaap_NetIncomeLoss	52,221us-gaap_NetIncomeLoss	347,261us-gaap_NetIncomeLoss	303,180us-gaap_NetIncomeLoss
Other comprehensive income (loss):
Foreign currency translation (pretax)	(3,213)	(3,325)	(6,752)	(5,530)
Foreign currency translation (tax effect)	0	0	0	0
Foreign currency translation (net of tax)	(3,213)	(3,325)	(6,752)	(5,530)
Unrealized gain (loss) on investments (pretax)	(2,959)	(2,251)	44,183	(43,257)
Unrealized gain (loss) on investments (tax effect)	1,036	766	(15,464)	15,020
Unrealized gain (loss) on investments (net of tax)	(1,923)	(1,485)	28,719	(28,237)
Change in fair value of cash flow hedges (pretax)	1,582	4,398	7,419	16,540
Change in fair value of cash flow hedges (tax effect)	(602)	(1,671)	(2,820)	(6,285)
Change in fair value of cash flow hedges (net of tax)	980	2,727	4,599	10,255
Total comprehensive income (loss) (pretax)	102,843	81,188	594,212	446,015
Total comprehensive income (loss) (tax effect)	(40,459)us-gaap_OtherComprehensiveIncomeLossTax	(31,050)us-gaap_OtherComprehensiveIncomeLossTax	(220,385)us-gaap_OtherComprehensiveIncomeLossTax	(166,347)us-gaap_OtherComprehensiveIncomeLossTax
Total comprehensive income (loss) (net of tax)	$ 62,384us-gaap_ComprehensiveIncomeNetOfTax	$ 50,138us-gaap_ComprehensiveIncomeNetOfTax	$ 373,827us-gaap_ComprehensiveIncomeNetOfTax	$ 279,668us-gaap_ComprehensiveIncomeNetOfTax

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