Variable Interest Entities - Carrying Amounts and Maximum Exposure to Loss for Non Consolidated VIEs (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Variable Interest Entity [Line Items]
Net Carrying Amount	$ 92.0	$ 151.6
Maximum Exposure to Loss	92.0	151.6
Investments in affiliates [Member]
Variable Interest Entity [Line Items]
Net Carrying Amount	91.3	72.2
Maximum Exposure to Loss	91.3	72.2
Leveraged leases [Member]
Variable Interest Entity [Line Items]
Net Carrying Amount		78.5
Maximum Exposure to Loss		78.5
Other investment [Member]
Variable Interest Entity [Line Items]
Net Carrying Amount	0.7	0.9
Maximum Exposure to Loss	$ 0.7	$ 0.9