Assets Measured at Fair Value on a Nonrecurring Basis (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Fair Value Measurements On Nonrecurring Basis [Line Items]
Impairment charges	$ 4.1	$ 9.4
Fair Value, Measurements, Nonrecurring
Fair Value Measurements On Nonrecurring Basis [Line Items]
Long-lived assets held and used, impairment charge	3.6	5.6
Long-lived assets held for sale or disposal, Impairment charge	1.1	3.8
Impairment charges	4.7	9.4
Long-lived assets held and used, net book value	1.6	4.2
Total	1.6	4.2
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	1.6	4.2
Long-lived assets held for sale or disposal, fair value measurement	0.4	1.5
Total, Fair value measurement	$ 2.0	$ 5.7