Stockholders' Equity (Schedule of Stockholders' Equity) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		1 Months Ended	3 Months Ended
		Jun. 30, 2015	Jun. 30, 2015		Jun. 30, 2014	Mar. 31, 2015
Class of Stock [Line Items]
Common stock, par value		$ 0.01	$ 0.01			$ 0.01
Common stock, shares issued		87,608	87,608			87,554
Common stock issuance	[1]		54
Treasury stock, shares		(13,034)	(13,034)			(12,197)
Reissuance of treasury stock for stock option exercises			163
Purchase of treasury stock		(1,000)	(1,000)	[2]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2015			$ 2,151,586
Net earnings			88,235		$ 88,852
Other comprehensive income (loss), net of tax			1,891		$ 2,656
Common stock issuances and reissuances of treasury stock - employee benefit plans	[3]		11,547
Purchase of treasury stock	[2]		(103,839)
Excess tax benefit from stock option exercises			3,891
Dividends paid on common stock ($0.60 per share)			(44,873)
Stock-based compensation	[4]		13,650
Balance at June 30, 2015		$ 2,122,088	$ 2,122,088
Dividends paid per common share			$ 0.60
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2015			$ 876
Issuance of common stock for purchases through the Employee Stock Purchase Plan	[3]		0
Balance at June 30, 2015		876	876
Capital In Excess of Par Value [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2015			853,800
Common stock issuances and reissuances of treasury stock - employee benefit plans	[3]		4,836
Excess tax benefit from stock option exercises			3,891
Stock-based compensation	[4]		13,650
Balance at June 30, 2015		876,177	876,177
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2015			2,231,026
Net earnings			88,235
Reissuance of treasury stock for stock option exercises at lower than repurchase price	[3]		(5,993)
Dividends paid on common stock ($0.60 per share)			(44,873)
Balance at June 30, 2015		2,268,395	2,268,395
Accumulated Other Comprehensive Income [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2015			(14,853)
Other comprehensive income (loss), net of tax			1,891
Balance at June 30, 2015		(12,962)	(12,962)
Treasury Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at March 31, 2015			(919,263)
Reissuance of treasury stock for stock option exercises	[3]		12,704
Purchase of treasury stock	[2]		(103,839)
Balance at June 30, 2015		$ (1,010,398)	$ (1,010,398)

[1] Issuance of common stock for purchases through the Amended and Restated 2003 Employee Stock Purchase Plan (“Employee Stock Purchase Plan” or “ESPP”).

[2] Refer to “Stock Repurchase Program” section below for details.

[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.