Cat Financial Financing Activities (Details) - Finance Receivables - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2018	Dec. 31, 2017
Allowance for Credit Loss Activity
Balance at beginning of year	$ 362	$ 341
Receivables written off	(181)	(157)
Recoveries on receivables previously written off	31	43
Provision for credit losses	214	128
Other	(14)	7
Balance at end of period	412	362
Allowance for Credit Losses
Individually evaluated for impairment			$ 229	$ 149
Collectively evaluated for impairment			183	213
Ending Balance	362	341	412	362
Recorded Investment in Finance Receivables
Individually evaluated for impairment			802	942
Collectively evaluated for impairment			21,660	21,690
Ending balance-recorded investment in finance receivables			22,462	22,632
Customer
Allowance for Credit Loss Activity
Balance at beginning of year	353	331
Receivables written off	(181)	(157)
Recoveries on receivables previously written off	31	43
Provision for credit losses	216	129
Other	(14)	7
Balance at end of period	405	353
Allowance for Credit Losses
Individually evaluated for impairment			229	149
Collectively evaluated for impairment			176	204
Ending Balance	353	331	405	353
Recorded Investment in Finance Receivables
Individually evaluated for impairment			802	942
Collectively evaluated for impairment			18,193	18,226
Ending balance-recorded investment in finance receivables			18,995	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	(2)	(1)
Other	0	0
Balance at end of period	7	9
Allowance for Credit Losses
Individually evaluated for impairment			0	0
Collectively evaluated for impairment			7	9
Ending Balance	$ 9	$ 10	7	9
Recorded Investment in Finance Receivables
Individually evaluated for impairment			0	0
Collectively evaluated for impairment			3,467	3,464
Ending balance-recorded investment in finance receivables			$ 3,467	$ 3,464

No definition available.

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Balance Type:	na
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- 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

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- Definition

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

+ References

+ Details

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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

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Balance Type:	credit
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- Definition

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

+ References

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- Definition

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

+ References

+ Details

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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

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Balance Type:	na
Period Type:	duration

- Definition

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

+ References

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

- Definition

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

+ References

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- Definition

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

+ References

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- 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://fasb.org/us-gaap/role/ref/legacyRef
-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

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-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5074-111524

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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://fasb.org/us-gaap/role/ref/legacyRef
-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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.11)
-URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260

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-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

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Balance Type:	debit
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