Share-Based Compensation Level 4 (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	9 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2011 years	Dec. 31, 2010 years
Share-based Compensation Arrangement by Share-based Payment Award [Line Item]
Remaining shares available for grant	4,568,661	4,568,661
Weighted-average assumptions used for options granted:
Risk-free interest rate		2.41%	2.68%
Expected life of options		5.65	5.65
Exptected dividend yield of stock		1.78%	1.59%
Expected volatility of stock		29.78%	30.13%
Estimated forfeiture rate		2.08%	2.27%
Summary of share option activity:
Number of Options, Outstanding, Beginning of Period		3,274,395
Weighted Average Exercise Price, Outstanding, Beginning of Period		$ 25.95
Number of Options, Granted		325,051
Weighted Average Exercise Price, Granted	$ 35.62	$ 35.62
Number of Options, Exercised		172,592
Weighted Average Exercise Price, Exercised	$ 22.38	$ 22.38
Number of Options, Forfeited		(11,084)
Weighted Average Exercise Price, Forfeited	$ 27.25	$ 27.25
Number of Options, Canceled		23,240
Weighted Average Exercise Price, Canceled	$ 22.93	$ 22.93
Number of Options, Outstanding, End of Period	3,392,530	3,392,530
Weighted Average Exercise Price, Outstanding, End of Period	$ 27.07	$ 27.07
Average Remaining Contractual Term, Outstanding	5.40	5.40
Aggregate Intrinsic Value, Outstanding	$ 12,354	$ 12,354
Number of Options, Exercisable	2,505,105	2,505,105
Weighted Average Exercise Price, Exercisable	$ 25.91	$ 25.91
Average Remaining Contractual Term, Exercisable	4.41
Aggregate Intrinsic Value, Exercisable	10,464	10,464
Non-vested stock options outstanding expected to vest	874,261	874,261
Common Stock, Fair Market Value Per Share	$ 29.82	$ 29.82
Total intrinsic value of stock options exercised		2,111	5,655
Net cash proceeds from the exercise of stock options		3,749	10,813
Tax benefit from stock option exercises		816	2,197
Weighted average grant date fair value of stock option grants, per share		$ 9.31	$ 8.80
Summary of non-vested restricted share activity:
Unrecognized compensation cost related to nonvested share-based compensation granted	13,115	13,115
Weighted average period for recognition of unrecognized compensation cost		2.42
Stock Appreciation Rights (SARs)
Summary of non-vested restricted share activity:
Number of Restricted Shares, Non-vested at Beginning of Period		400,951
Weighted-Average Grant Date Fair Value, Non-vested at Beginning of Period		$ 29.70
Number of Restricted Shares, Granted		231,215
Weighted-Average Grant Date Fair Value, Granted		$ 35.70
Number of Restricted Shares, Vested		(76,743)
Weighted-Average Grant Date Fair Value, Vested		$ 30.33
Number of Restricted Shares, Canceled		(11,910)
Weighted-Average Grant Date Fair Value, Canceled	$ 33.06	$ 33.06
Number of Restricted Shares, Non-vested at End of Period	543,513	543,513
Weighted-Average Grant Date Fair Value, Non-vested at End of Period	$ 32.09	$ 32.09
FairValueOfOutstandingStockAppreciationRights	763	763	1,111
Restricted Stock
Summary of non-vested restricted share activity:
Fair Value, Share-based Payment Awards, Other than Options		2,328
Restricted Stock Units (RSUs)
Summary of non-vested restricted share activity:
FairValueOfOutstandingCashSettledRestrictedShareUnits	$ 1,244	$ 1,244	$ 1,282