Long-term Debt - U.S. Bank Debt (Details) (USD $) In Millions, unless otherwise specified								3 Months Ended
	Mar. 31, 2013	Mar. 31, 2013 U.S. bank debt and receivables facility [Member]	Dec. 31, 2012 U.S. bank debt and receivables facility [Member]	Mar. 31, 2013 Revolving credit and term loan facilities [Member]	Mar. 31, 2013 Senior Secured Term Loan B [Member]	Mar. 31, 2012 Medium-term Notes [Member]	Mar. 31, 2013 Senior Secured Term Loan A [Member]	Mar. 31, 2013 Senior Secured Term Loan B [Member]	Mar. 31, 2013 Revolving credit facility [Member]	Dec. 31, 2012 Revolving credit facility [Member]	Mar. 31, 2013 Letters of credit [Member]	Dec. 31, 2012 Letters of credit [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 2 [Member] Senior Secured Term Loan A [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Senior Secured Term Loan A [Member]	Mar. 31, 2013 Fair Value, Inputs, Level 2 [Member] Senior Secured Term Loan B [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Senior Secured Term Loan B [Member]
Debt Instrument [Line Items]
Revolving Credit Facility, Maximum Borrowing Capacity									$ 250.0
Debt Instrument, Basis Spread on Variable Rate							2.00%	2.75%	2.00%
Debt Instrument, Face Amount							200.0	200.0
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum								1.00%
Incremental debt commitments capacity				300
Net leverage ratio	2.50
Term Loan Facility, Required Prepay Premium					1.00%
Term Loan Facility, Required Prepay Portion Under Excess Cash Flow Sweep Provision [Line Items]						5.0
Letters of Credit, Maximum Borrowing Capacity											75.0
Letters of Credit Outstanding, Amount											23.6	23.3
Revolving Credit Facility, Amount Outstanding									30.0	0
Revolving Credit Facility, Remaining Borrowing Capacity									196.4	226.7
Debt Instrument, Unused Borrowing Capacity, Amount		$ 156.1	$ 230.5
Long-term Debt, Fair Value, % of par value													99.50%	99.30%	100.00%	99.90%