Cat Financial Financing Activities (Details) - Finance Receivables - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2018	Dec. 31, 2017
Allowance for Credit Loss Activity
Balance at beginning of year	$ 362	$ 341
Receivables written off	(40)	(157)
Recoveries on receivables previously written off	10	43
Provision for credit losses	66	128
Other	1	7
Balance at end of period	399	362
Allowance for Credit Losses
Individually evaluated for impairment			$ 194	$ 149
Collectively evaluated for impairment			205	213
Ending Balance	362	341	399	362
Recorded Investment in Finance Receivables
Individually evaluated for impairment			971	942
Collectively evaluated for impairment			21,531	21,690
Ending balance-recorded investment in finance receivables			(22,502)	(22,632)
Customer
Allowance for Credit Loss Activity
Balance at beginning of year	353	331
Receivables written off	(40)	(157)
Recoveries on receivables previously written off	10	43
Provision for credit losses	66	129
Other	1	7
Balance at end of period	390	353
Allowance for Credit Losses
Individually evaluated for impairment			194	149
Collectively evaluated for impairment			196	204
Ending Balance	353	331	390	353
Recorded Investment in Finance Receivables
Individually evaluated for impairment			971	942
Collectively evaluated for impairment			18,164	18,226
Ending balance-recorded investment in finance receivables			(19,135)	(19,168)
Dealer
Allowance for Credit Loss Activity
Balance at beginning of year	9	10
Receivables written off	0	0
Recoveries on receivables previously written off	0	0
Provision for credit losses	0	(1)
Other	0	0
Balance at end of period	9	9
Allowance for Credit Losses
Individually evaluated for impairment			0	0
Collectively evaluated for impairment			9	9
Ending Balance	$ 9	$ 10	9	9
Recorded Investment in Finance Receivables
Individually evaluated for impairment			0	0
Collectively evaluated for impairment			3,367	3,464
Ending balance-recorded investment in finance receivables			$ (3,367)	$ (3,464)

No definition available.

Name:	cat_FinanceReceivableRecordedInvestmentAbstract
Namespace Prefix:	cat_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the other activity, net, in the allowance for credit loss during the period not otherwise defined in the taxonomy.

+ References

No definition available.

+ Details

Name:	cat_FinancingReceivableAllowanceForCreditLossesOtherActivity
Namespace Prefix:	cat_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

A valuation allowance for financing receivables that are expected to be uncollectible.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of recovery of financing receivables doubtful of collection that were previously charged off.

+ References

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Definition

Amount of direct write-downs of financing receivables charged against the allowance.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The balance of financing receivables that were individually evaluated for impairment.

+ References

+ Details

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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 FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

Reference 2: 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=84173941&loc=d3e5074-111524

+ Details

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

- Definition

Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.11)
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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Namespace Prefix:	us-gaap_
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Balance Type:	debit
Period Type:	duration

- Details

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Namespace Prefix:
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- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=cat_CustomerMember
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- Details

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