Finance Receivables (Allowance For Credit Losses And Finance Receivables By Portfolio Individually And Collectively Evaluated For Impairment) (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Apr. 01, 2012	Dec. 31, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	$ 106,792	$ 107,667	$ 122,503	$ 125,449
Finance receivables, gross	6,140,731	5,889,519	5,999,906
Individually Evaluated For Impairment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	0	0	0
Finance receivables, gross	0	0	0
Collectively Evaluated For Impairment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	106,792	107,667	122,503
Finance receivables, gross	6,140,731	5,889,519	5,999,906
Retail [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	98,542	101,442	112,857
Finance receivables, gross	4,981,488	5,073,115	5,043,584
Retail [Member] \| Individually Evaluated For Impairment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	0	0	0
Finance receivables, gross	0	0	0
Retail [Member] \| Collectively Evaluated For Impairment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	98,542	101,442	112,857
Finance receivables, gross	4,981,488	5,073,115	5,043,584
Wholesale [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	8,250	6,225	9,646
Finance receivables, gross	1,159,243	816,404	956,322
Wholesale [Member] \| Individually Evaluated For Impairment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	0	0	0
Finance receivables, gross	0	0	0
Wholesale [Member] \| Collectively Evaluated For Impairment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses	8,250	6,225	9,646
Finance receivables, gross	$ 1,159,243	$ 816,404	$ 956,322

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 8, 9

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (b)(1)(ii)

-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(d))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Section 563c.102

-Paragraph 8

-Subparagraph a(ii)

-Chapter V

-Subsection I

-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph d

-Article 9

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 114

-Paragraph 20

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section L

-Subsection 1

+ Details