Asset-Backed Financing (Narrative) (Detail) (USD $)	3 Months Ended			3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012 SPEs [Member]	Apr. 01, 2012 SPEs [Member]	Mar. 31, 2013 Asset-backed Canadian Commercial Paper Conduit Facility [Member]
Variable Interest Entity [Line Items]
Maximum Borrowing Capacity Under Conduit Facility				$ 200,000,000
Unaccreted premium	1,000,000
Asset-backed securities expiration date	9/13/2013
Total aggregate commitment	600,000,000
Borrowings outstanding under conduit facility		0	0
Line of Credit Facility, Expiration Date				Aug. 30, 2013
Maturity Date Of Debt Instrument				5 years
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 28,400,000