Share-Based Compensation Level 4 (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	6 Months Ended
	Sep. 30, 2012 years	Sep. 30, 2012 years	Sep. 30, 2011 years
Share-based Compensation Arrangement by Share-based Payment Award [Line Item]
Remaining shares available for grant	3,911,745	3,911,745
Weighted-average assumptions used for options granted:
Risk-free interest rate		1.21%	2.41%
Expected life of options		5.79	5.65
Exptected dividend yield of stock		2.15%	1.78%
Expected volatility of stock		31.24%	29.78%
Estimated forfeiture rate		1.83%	2.08%
Summary of share option activity:
Number of Options, Outstanding, Beginning of Period		3,312,602
Weighted Average Exercise Price, Outstanding, Beginning of Period		$ 27.16
Number of Options, Granted		299,665
Weighted Average Exercise Price, Granted	$ 30.25	$ 30.25
Number of Options, Exercised		(509,271)
Weighted Average Exercise Price, Exercised	$ 23.89	$ 23.89
Number of Options, Forfeited		(5,933)
Weighted Average Exercise Price, Forfeited	$ 30.12	$ 30.12
Number of Options, Canceled		3,970
Weighted Average Exercise Price, Canceled	$ 19.95	$ 19.95
Number of Options, Outstanding, End of Period	3,093,093	3,093,093
Weighted Average Exercise Price, Outstanding, End of Period	$ 28.00	$ 28.00
Average Remaining Contractual Term, Outstanding	5.58	5.58
Aggregate Intrinsic Value, Outstanding	$ 23,292	$ 23,292
Number of Options, Exercisable	2,320,680	2,320,680
Weighted Average Exercise Price, Exercisable	$ 27.05	$ 27.05
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	4.59
Aggregate Intrinsic Value, Exercisable	19,601	19,601
Non-vested stock options outstanding expected to vest	758,578	758,578
Common Stock, Fair Market Value Per Share	$ 35.47	$ 35.47
Total intrinsic value of stock options exercised		4,594	1,927
Net cash proceeds from the exercise of stock options		11,709	3,172
Tax benefit from stock option exercises		1,772	745
Weighted average grant date fair value of stock option grants, per share		$ 7.31	$ 9.84
Summary of non-vested restricted share activity:
Unrecognized compensation cost related to nonvested share-based compensation granted	17,662	17,662
Weighted average period for recognition of unrecognized compensation cost		2.65
Stock Appreciation Rights (SARs) [Member]
Summary of non-vested restricted share activity:
FairValueOfOutstandingStockAppreciationRights	928	928	807
Restricted Stock
Summary of non-vested restricted share activity:
Number of Restricted Shares, Non-vested at Beginning of Period		533,027
Weighted-Average Grant Date Fair Value, Non-vested at Beginning of Period		$ 32.10
Number of Restricted Shares, Granted		273,767
Weighted-Average Grant Date Fair Value, Granted		$ 30.51
Number of Restricted Shares, Vested		(100,320)
Weighted-Average Grant Date Fair Value, Vested		$ 24.78
Number of Restricted Shares, Canceled		(8,385)
Weighted-Average Grant Date Fair Value, Canceled	$ 33.15	$ 33.15
Number of Restricted Shares, Non-vested at End of Period	698,089	698,089
Weighted-Average Grant Date Fair Value, Non-vested at End of Period	$ 32.52	$ 32.52
Fair Value, Share-based Payment Awards, Other than Options		2,486
Restricted Stock Units (RSUs)
Summary of non-vested restricted share activity:
FairValueOfOutstandingCashSettledRestrictedShareUnits	$ 1,233	$ 1,233	$ 1,239