Debt - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended						1 Months Ended	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2012 CPT	Mar. 31, 2012 Maximum	Mar. 31, 2012 Fair Value, Inputs, Level 2	Dec. 31, 2011 Fair Value, Inputs, Level 2	Apr. 02, 2011 Fair Value, Inputs, Level 2	Apr. 30, 2011 Credit Facility	Mar. 31, 2012 Credit Facility	Mar. 31, 2012 Other Credit Facilities	May 31, 2011 Senior Notes, 5.000 Percent Due 2021	Mar. 31, 2012 Private Placement Debt Due May 2012
Debt Disclosure [Line Items]
Fair value of total debt				$ 1,482.5	$ 1,361.0	$ 838.9
Aggregate principal amount										500
Debt, interest rate										5.00%
Debt, maturity year										2021
Previous revolving credit facility							800
Credit facility maximum borrowing capacity							700.0		75.3
Credit facility expiration date							2016-04-28
Credit facility interest rate, before the addition of LIBOR							1.75%
Remaining availability under the Credit Facility								435.7
Remaining availability under the Credit Facility limited by leverage ratio								362.2
Debt agreement financial covenant, leverage ratio that may not exceeded by reported date			3.5
Compliance with debt agreement financial covenants	We were in compliance with all financial covenants in our debt agreements as of March 31, 2012.
Line of credit facility, amount outstanding									28.1
Long-term debt, outstanding											105
Long-term debt, maturity date											2012-05
Capital lease obligation cost		23.4
Accumulated amortization		5.3
Future minimum lease payments	18.0
Imputed interest	$ 2.0