Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Schedule of Residual Interests Securitized Receivables and Derivatives Carried at Fair Value (Detail)

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Fair Value Measurements - Schedule of Residual Interests Securitized Receivables and Derivatives Carried at Fair Value (Detail) (Fair Value, Measurements, Recurring [Member], Level 3 [Member], USD $)
In Millions, unless otherwise specified
Sep. 30, 2014
Dec. 31, 2013
Fair Value [Member] | Credit Facility [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Liabilities $ 212.8 $ 77.1
Fair Value [Member] | Nonrecourse Debt [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Liabilities 132.3 167.1
Fair Value [Member] | Asset-Backed Nonrecourse Notes [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Liabilities 92.9 99.8
Fair Value [Member] | Financing Receivable [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets 507.2 346.4
Fair Value [Member] | Investments Available-for-sale [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets 43.4 3.2
Fair Value [Member] | Residual Assets [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets 5.0 4.9
Fair Value [Member] | Investments [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets   92.0
Fair Value [Member] | Financing Receivables Held For Sale [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets 7.2 24.8
Carrying Value [Member] | Credit Facility [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Liabilities 212.8 77.1
Carrying Value [Member] | Nonrecourse Debt [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Liabilities 118.3 159.8
Carrying Value [Member] | Asset-Backed Nonrecourse Notes [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Liabilities 93.6 100.0
Carrying Value [Member] | Financing Receivable [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets 477.9 347.9
Carrying Value [Member] | Investments Available-for-sale [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets 43.4 3.2
Carrying Value [Member] | Residual Assets [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets 5.0 4.9
Carrying Value [Member] | Investments [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets   92.0
Carrying Value [Member] | Financing Receivables Held For Sale [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets $ 7.2 $ 24.8