Stockholders' Equity (Schedule of Stockholders' Equity) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Jun. 30, 2014		Jun. 30, 2013	Mar. 31, 2014
Class of Stock [Line Items]
Common stock, shares issued	87,408			87,353
Common stock issuance during period, shares, Employee Stock Purchase Plan	55	[1]
Treasury stock, shares	(12,948)			(13,264)
Reissuance of treasury stock for stock option exercises	275
Reissuance of treasury stock for acquisition	41
Dividends paid per common share	$ 0.55
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2014	$ 1,840,649
Net earnings	88,852		84,686
Other comprehensive income, net of tax	2,656		(2,484)
Common stock issuances and reissuances of treasury stock - employee benefit plans	16,180	[2]
Reissuance of treasury stock for acquisition (Note 3)	4,458
Excess tax benefit from stock option exercises	4,063
Dividends paid on common stock	(40,914)		(35,202)
Stock-based compensation	14,830	[3]
Balance at June 30, 2014	1,930,774
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2014	874
Issuance of common stock for purchases through the Employee Stock Purchase Plan	0	[2]
Balance at June 30, 2014	874
Capital In Excess of Par Value [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2014	789,789
Issuance of common stock for purchases through the Employee Stock Purchase Plan	4,602	[2]
Reissuance of treasury stock for acquisition (Note 3)	1,368
Excess tax benefit from stock option exercises	4,063
Stock-based compensation	14,830	[3]
Balance at June 30, 2014	814,652
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2014	2,047,843
Net earnings	88,852
Reissuance of treasury stock for stock option exercises at lower than repurchase price	(7,123)	[2]
Dividends paid on common stock	(40,914)
Balance at June 30, 2014	2,088,658
Accumulated Other Comprehensive Income [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2014	529
Other comprehensive income, net of tax	2,656
Balance at June 30, 2014	3,185
Treasury Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2014	(998,386)
Reissuance of treasury stock for stock option exercises	18,701	[2]
Reissuance of treasury stock for acquisition (Note 3)	3,090
Balance at June 30, 2014	$ (976,595)

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

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

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