Retirement Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2012 Rate	Mar. 31, 2011	Mar. 31, 2010
Retirement Plans (Textual) [Abstract]
Costs of employer matching contributions to 401(k) plan	$ 16.9	$ 16.4	$ 14.5
Period to fully vest 401(k) employer matching contributions	two years of service from date of hire
Maximum vesting percentage of 401(k) employer matching contributions	100.00%
Amounts included in other long-term liabilities related to the non-qualified deferred compensation plan	$ 19.7	$ 18.8