Asset-Backed Financing (Assets And Liabilities Of Variable Interest Entities) (Detail) (USD $)	Mar. 31, 2013	Dec. 31, 2012	Apr. 01, 2012	Dec. 31, 2011
Variable Interest Entity [Line Items]
Line of credit facility, maximum borrowing capacity	$ 600,000,000
Loans and Leases Receivable, Allowance	106,792,000	107,667,000	122,503,000	125,449,000
Restricted cash	197,025,000	188,008,000	246,995,000
SPEs [Member]
Variable Interest Entity [Line Items]
Restricted cash	185,657,000	176,290,000	246,995,000
SPEs Facility [Member]
Variable Interest Entity [Line Items]
Restricted cash	0
Asset-backed Securities [Member]
Variable Interest Entity [Line Items]
Finance receivables	2,045,839,000	2,337,993,000	2,575,274,000
Loans and Leases Receivable, Allowance	39,722,000	45,571,000	57,046,000
Restricted cash	197,025,000	188,008,000	246,995,000
Other assets	5,396,000	5,543,000	5,932,000
Total assets	2,208,538,000	2,485,973,000	2,771,155,000
Secured Debt	1,423,168,000	1,623,434,000	1,754,320,000
Asset-backed Securities [Member] | SPEs [Member]
Variable Interest Entity [Line Items]
Finance receivables	1,871,419,000	2,143,708,000	2,564,585,000
Loans and Leases Receivable, Allowance	36,799,000	42,139,000	56,810,000
Restricted cash	185,657,000	176,290,000	245,912,000
Other assets	4,935,000	4,869,000	5,620,000
Total assets	2,025,212,000	2,282,728,000	2,759,307,000
Secured Debt	1,268,572,000	1,447,776,000	1,754,320,000
Asset-backed U.S. Commercial Paper Conduit Facility [Member] | SPEs [Member]
Variable Interest Entity [Line Items]
Finance receivables	0	0	10,689,000
Loans and Leases Receivable, Allowance	0	0	236,000
Restricted cash	0	0	1,083,000
Other assets	294,000	419,000	312,000
Total assets	294,000	419,000	11,848,000
Secured Debt	0	0	0
Asset-backed Canadian Commercial Paper Conduit Facility [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Finance receivables	174,420,000	194,285,000	0
Loans and Leases Receivable, Allowance	2,923,000	3,432,000	0
Restricted cash	11,368,000	11,718,000	0
Other assets	167,000	255,000	0
Total assets	183,032,000	202,826,000	0
Secured Debt	$ 154,596,000	$ 175,658,000	$ 0