Assets Measured at Fair Value on a Nonrecurring Basis (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Fair Value Measurements On Nonrecurring Basis [Line Items]
Impairment charges			$ 7.8	$ 18.0
Fair Value, Measurements, Nonrecurring
Fair Value Measurements On Nonrecurring Basis [Line Items]
Long-lived assets held and used, impairment charge	0.3	1.6	0.8	7.2
Long-lived assets held for sale or disposal, impairment charge	3.4	7.6	7.6	11.4
Impairment charges	3.7	9.2	8.4	18.6
Long-lived assets held and used, net book value	0.5	8.7	0.5	8.7
Long-lived assets held for sale or disposal, net book value	12.1	8.1	12.1	8.1
Total	12.6	16.8	12.6	16.8
Fair Value, Measurements, Nonrecurring | Fair Value, Inputs, Level 3
Fair Value Measurements On Nonrecurring Basis [Line Items]
Long-lived assets held and used, fair value measurement	0.3	4.9	0.6	9.1
Long-lived assets held for sale or disposal, fair value measurement	12.2	9.2	13.9	10.7
Total, Fair value measurement	$ 12.5	$ 14.1	$ 14.5	$ 19.8