Long-Term Borrowings (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Dec. 31, 2011	Mar. 31, 2011	Nov. 30, 2010
Long-Term Borrowings
Senior unsecured notes due 2018 (net of $1.1 million and $1.3 million of unamortized discount as of December 31, 2011 and March 1, 2011, respectively)	$ 298.9	$ 298.7
Capital leases and other obligations	47.6	56.2
Total	346.5	354.9
Less current maturities of capital leases and other obligations (included in accrued liabilities)	(21.1)	(19.3)
Long-term borrowings	325.4	335.6
Long-Term Borrowings (Textual) [Abstract]
Maximum amount of credit facility			600.0
Unamortized discount	1.1	1.3
Expiration date of credit facility	Nov. 30, 2014
Amount of unsecured revolving credit facility			400.0
Provision for swing line loans (maximum)			25.0
Provision for standby letters of credit (maximum)			$ 50.0
Period One [Member]
Debt Instrument [Line Items]
Interest periods for revolving loans under the credit facility	1 month
Period Two [Member]
Debt Instrument [Line Items]
Interest periods for revolving loans under the credit facility	2 months
Period Three [Member]
Debt Instrument [Line Items]
Interest periods for revolving loans under the credit facility	3 months
Period Four [Member]
Debt Instrument [Line Items]
Interest periods for revolving loans under the credit facility	6 months