Stockholders' Equity (Schedule of Stockholders' Equity) (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012		Dec. 31, 2011	Mar. 31, 2012
Class of Stock [Line Items]
Common stock, shares, issued	87,074		87,074			86,874
Common stock issuance during period, shares, Employee Stock Purchase Plans			200	[1]
Treasury stock, shares	10,514		10,514			10,207
Reissuance of treasury stock for stock option exercises, shares			(2,164)
Purchase of treasury stock			2,471	[2]
Common Stock, Dividends, Per Share, Cash Paid			$ 1.20
Stock Repurchase Program, Authorized Amount	$ 600,000,000
Treasury Stock Acquired, Average Cost Per Share	$ 89.93
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2012			1,750,258,000
Net earnings	82,915,000	72,558,000	254,733,000		225,406,000
Other comprehensive income	(54,000)	669,000	605,000		(4,779,000)
Stock Issued During Period, Value, Employee Stock Purchase Plan			90,872,000	[3]
Tax benefit from stock option exercises			33,352,000
Dividends paid on common stock ($1.20 per share)			(92,655,000)		(70,819,000)
Stock-based compensation			22,744,000	[4]
Purchase of treasury stock			(222,163,000)	[2]
Balance at December 31, 2012	1,837,746,000		1,837,746,000
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2012			869,000
Stock Issued During Period, Value, Employee Stock Purchase Plan			2,000	[3]
Balance at December 31, 2012	871,000		871,000
Capital In Excess of Par Value [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2012			649,551,000
Stock Issued During Period, Value, Employee Stock Purchase Plan			12,779,000	[3]
Tax benefit from stock option exercises			33,352,000
Stock-based compensation			22,744,000	[4]
Balance at December 31, 2012	718,426,000		718,426,000
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2012			1,701,478,000
Net earnings			254,733,000
Stock Issued During Period, Value, Treasury Stock Reissued			(52,135,000)	[3]
Dividends paid on common stock ($1.20 per share)			(92,655,000)
Balance at December 31, 2012	1,811,421,000		1,811,421,000
Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2012			5,386,000
Other comprehensive income			605,000
Balance at December 31, 2012	5,991,000		5,991,000
Treasury Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2012			(607,026,000)
Stock Issued During Period, Value, Treasury Stock Reissued			130,226,000	[3]
Purchase of treasury stock			(222,163,000)	[2]
Balance at December 31, 2012	$ (698,963,000)		$ (698,963,000)

[1] Issuance of common stock for purchases through the Employee Stock Purchase Plan.

[2] On October 23, 2012, the Company announced a $600 million share repurchase program. During the three months ended December 31, 2012, the Company repurchased 2.47 million shares on the open market at an average price of $89.93.

[3] Issuance of common stock for purchases through the Employee Stock Purchase Plan and reissuance of treasury stock for stock option exercises.

[4] The Company recognized compensation expense with a corresponding amount recorded to capital in excess of par value.