Cat Financial Financing Activities (Details 2) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2012	Dec. 31, 2011
Receivables [Abstract]
Period after which Unpaid Installments are Considered as Past Due (in days)	30 days
Period after which collection of future income is considered as not probable (in days)	120 days
Aging related to loans and finance leases
31-60 Days Past Due	$ 213	$ 194
61-90 Days Past Due	115	104
91+ Days Past Due	473	442
Total Past Due	801	740
Current	21,619	19,240
Total Financing Receivable, Gross	22,420	19,980
91+ Still Accruing	34	58
North America
Aging related to loans and finance leases
Total Financing Receivable, Gross	7,755	7,291
Europe
Aging related to loans and finance leases
Total Financing Receivable, Gross	2,533	2,281
Asia Pacific
Aging related to loans and finance leases
Total Financing Receivable, Gross	3,745	3,038
Mining
Aging related to loans and finance leases
Total Financing Receivable, Gross	1,840	1,485
Latin America
Aging related to loans and finance leases
Total Financing Receivable, Gross	3,384	2,965
Caterpillar Power Finance
Aging related to loans and finance leases
Total Financing Receivable, Gross	3,163	2,920
Customer
Aging related to loans and finance leases
Total Financing Receivable, Gross	19,041	17,593
Investment in loans and finance leases on non-accrual status	609	472
Customer \| North America
Aging related to loans and finance leases
31-60 Days Past Due	35	74
61-90 Days Past Due	9	39
91+ Days Past Due	76	111
Total Past Due	120	224
Current	5,665	5,378
Total Financing Receivable, Gross	5,785	5,602
91+ Still Accruing	0	9
Investment in loans and finance leases on non-accrual status	77	112
Customer \| Europe
Aging related to loans and finance leases
31-60 Days Past Due	28	27
61-90 Days Past Due	12	11
91+ Days Past Due	44	57
Total Past Due	84	95
Current	2,371	2,129
Total Financing Receivable, Gross	2,455	2,224
91+ Still Accruing	5	10
Investment in loans and finance leases on non-accrual status	44	58
Customer \| Asia Pacific
Aging related to loans and finance leases
31-60 Days Past Due	74	47
61-90 Days Past Due	22	23
91+ Days Past Due	51	38
Total Past Due	147	108
Current	2,956	2,769
Total Financing Receivable, Gross	3,103	2,877
91+ Still Accruing	17	14
Investment in loans and finance leases on non-accrual status	40	24
Customer \| Mining
Aging related to loans and finance leases
31-60 Days Past Due	2	0
61-90 Days Past Due	0	0
91+ Days Past Due	12	12
Total Past Due	14	12
Current	1,825	1,473
Total Financing Receivable, Gross	1,839	1,485
91+ Still Accruing	0	0
Investment in loans and finance leases on non-accrual status	12	12
Customer \| Latin America
Aging related to loans and finance leases
31-60 Days Past Due	57	32
61-90 Days Past Due	25	15
91+ Days Past Due	136	99
Total Past Due	218	146
Current	2,478	2,339
Total Financing Receivable, Gross	2,696	2,485
91+ Still Accruing	0	0
Investment in loans and finance leases on non-accrual status	150	108
Customer \| Caterpillar Power Finance
Aging related to loans and finance leases
31-60 Days Past Due	17	14
61-90 Days Past Due	47	16
91+ Days Past Due	154	125
Total Past Due	218	155
Current	2,945	2,765
Total Financing Receivable, Gross	3,163	2,920
91+ Still Accruing	12	25
Investment in loans and finance leases on non-accrual status	286	158
Dealer
Aging related to loans and finance leases
Total Financing Receivable, Gross	3,379	2,387
Investment in loans and finance leases on non-accrual status	0	0
Dealer \| North America
Aging related to loans and finance leases
31-60 Days Past Due
61-90 Days Past Due
91+ Days Past Due
Total Past Due	0	0
Current	1,970	1,689
Total Financing Receivable, Gross	1,970	1,689
91+ Still Accruing
Dealer \| Europe
Aging related to loans and finance leases
31-60 Days Past Due
61-90 Days Past Due
91+ Days Past Due
Total Past Due	0	0
Current	78	57
Total Financing Receivable, Gross	78	57
91+ Still Accruing
Dealer \| Asia Pacific
Aging related to loans and finance leases
31-60 Days Past Due
61-90 Days Past Due
91+ Days Past Due
Total Past Due	0	0
Current	642	161
Total Financing Receivable, Gross	642	161
91+ Still Accruing
Dealer \| Mining
Aging related to loans and finance leases
31-60 Days Past Due
61-90 Days Past Due
91+ Days Past Due
Total Past Due	0
Current	1
Total Financing Receivable, Gross	1	0
91+ Still Accruing
Dealer \| Latin America
Aging related to loans and finance leases
31-60 Days Past Due
61-90 Days Past Due
91+ Days Past Due
Total Past Due	0	0
Current	688	480
Total Financing Receivable, Gross	688	480
91+ Still Accruing
Dealer \| Caterpillar Power Finance
Aging related to loans and finance leases
Total Financing Receivable, Gross	$ 0	$ 0

Financing receivables that are less than 61 days past due but more than 30 days past due.

No definition available.

Name:	cat_FinancingReceivableRecordedInvestment31To60DaysPastDue
Namespace Prefix:	cat_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Financing receivables that are less than 91 days past due but more than 60 days past due.

+ References

No definition available.

+ Details

Name:	cat_FinancingReceivableRecordedInvestment61To90DaysPastDue
Namespace Prefix:	cat_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Recorded investment in financing receivables that are 91 days or more past due and still accruing.

+ References

No definition available.

+ Details

Name:	cat_FinancingReceivableRecordedInvestment91DaysPastDueAndStillAccruing
Namespace Prefix:	cat_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Financing receivables that are more than 91 days past due.

+ References

No definition available.

+ Details

Name:	cat_FinancingReceivableRecordedInvestmentGreaterThan91DaysPastDue
Namespace Prefix:	cat_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the period after which collection of future income is considered as not probable.

+ References

No definition available.

+ Details

Name:	cat_PeriodAfterWhichCollectionOfFutureIncomeIsConsideredAsNotProbable
Namespace Prefix:	cat_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the period after which the unpaid contractual payments are considered as past due.

+ References

No definition available.

+ Details

Name:	cat_PeriodAfterWhichUnpaidInstallmentsAreConsideredAsPastDue
Namespace Prefix:	cat_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Financing receivables that are current.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7A

-URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953401-111524

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Recorded Investment in financing receivables that are past due at the balance sheet date.

+ References

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentPastDue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentPastDueAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Reflects the carrying amount of loans deemed to be questionable as to collection on which no interest is continuing to be recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5111-111524

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

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 01-6

-Paragraph 13

-Subparagraph g

-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.

+ Details

Name:	us-gaap_LoansAndLeasesReceivableImpairedNonperformingNonaccrualOfInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

+ References

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

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Section 563c.102

-Paragraph 8

-Subparagraph e

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

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-DEP

-Paragraph 116

-IssueDate 2006-05-01

-Chapter 8

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5074-111524

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6375948&loc=d3e4428-111522

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

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 01-6

-Paragraph 13

-Subparagraph e

-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.

+ Details

Name:	us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_ReceivablesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration