Debt instrument percentage of face value.

No definition available.

Name:	itw_DebtInstrumentPercentageOfFaceValue
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Period Type:	instant

- Definition

Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(13)(2))
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
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+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585

+ Details

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

- Definition

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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+ Details

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

- Definition

Weighted average interest rate of short-term debt outstanding calculated at point in time.

+ References

+ Details

Name:	us-gaap_ShortTermDebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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- Details

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Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_UnsecuredDebtMember
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Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=itw_A6.25NotesDueApril12019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=itw_LineofCreditTerminatingMay92021Member
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Balance Type:
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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Debt - Narrative (Details)		3 Months Ended
Debt - Narrative (Details)	Feb. 25, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Nov. 30, 2016 USD ($)	May 31, 2015 EUR (€)	May 31, 2014 EUR (€)	Feb. 28, 2014 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2005 USD ($)
Line of Credit Facility [Line Items]
Commercial paper			$ 0	$ 849,000,000
1.95% notes due March 1, 2019
Line of Credit Facility [Line Items]
Short term debt			$ 650,000,000
Interest rate, stated percentage			1.95%
1.95% notes due March 1, 2019 \| Unsecured debt
Line of Credit Facility [Line Items]
Interest rate, stated percentage			1.95%					1.95%
Face value of notes								$ 650,000,000
Notes issued, percentage of face value								99.871%
6.25% notes due April 1, 2019
Line of Credit Facility [Line Items]
Short term debt			$ 700,000,000
Interest rate, stated percentage			6.25%
6.25% notes due April 1, 2019 \| Unsecured debt
Line of Credit Facility [Line Items]
Interest rate, stated percentage			6.25%								6.25%
Face value of notes											$ 700,000,000
Notes issued, percentage of face value											99.98%
Line of credit terminating May 9, 2021
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity		$ 2,500,000,000.0
Debt Instrument, term		5 years
Line of credit, amounts outstanding			$ 0
4.88% notes due thru December 31, 2020 \| Unsecured debt
Line of Credit Facility [Line Items]
Interest rate, stated percentage			4.88%									4.88%
Face value of notes												$ 54,000,000
Notes issued, percentage of face value												100.00%
3.375% notes due September 15, 2021 \| Unsecured debt
Line of Credit Facility [Line Items]
Interest rate, stated percentage			3.375%							3.375%
Face value of notes										$ 350,000,000
Notes issued, percentage of face value										99.552%
4.875% notes due September 15, 2041 \| Unsecured debt
Line of Credit Facility [Line Items]
Interest rate, stated percentage			4.875%							4.875%
Face value of notes										$ 650,000,000
Notes issued, percentage of face value										98.539%
3.9% notes due September 1, 2042 \| Unsecured debt
Line of Credit Facility [Line Items]
Interest rate, stated percentage			3.90%						3.90%
Face value of notes									$ 1,100,000,000.0
Notes issued, percentage of face value									99.038%
0.90% notes due February 25, 2017 \| Unsecured debt
Line of Credit Facility [Line Items]
Interest rate, stated percentage	0.90%							0.90%
Face value of notes								$ 650,000,000
Notes issued, percentage of face value								99.861%
Repayments of debt	$ 650,000,000
3.50% notes due March 1, 2024 \| Unsecured debt
Line of Credit Facility [Line Items]
Interest rate, stated percentage			3.50%					3.50%
Face value of notes								$ 700,000,000
Notes issued, percentage of face value								99.648%
1.75% Euro notes due May 20, 2022 \| Unsecured debt
Line of Credit Facility [Line Items]
Interest rate, stated percentage			1.75%				1.75%
Face value of notes \| €							€ 500,000,000
Notes issued, percentage of face value							99.16%
3.0% Euro notes due May 19, 2034 \| Unsecured debt
Line of Credit Facility [Line Items]
Interest rate, stated percentage			3.00%				3.00%
Face value of notes \| €							€ 500,000,000
Notes issued, percentage of face value							98.089%
1.25% Euro notes due May 22, 2023 \| Unsecured debt
Line of Credit Facility [Line Items]
Interest rate, stated percentage			1.25%			1.25%
Face value of notes \| €						€ 500,000,000
Notes issued, percentage of face value						99.239%
2.125% Euro notes due May 22, 2030 \| Unsecured debt
Line of Credit Facility [Line Items]
Interest rate, stated percentage			2.125%			2.125%
Face value of notes \| €						€ 500,000,000
Notes issued, percentage of face value						99.303%
2.65% notes due November 15, 2026 \| Unsecured debt
Line of Credit Facility [Line Items]
Interest rate, stated percentage			2.65%		2.65%
Face value of notes					$ 1,000,000,000.0
Notes issued, percentage of face value					99.685%
Net investment hedging \| Unsecured debt
Line of Credit Facility [Line Items]
Face value of notes \| €						€ 1,000,000,000.0	€ 1,000,000,000
Commercial paper
Line of Credit Facility [Line Items]
Weighted average interest rate			1.70%	1.00%
Line of credit \| International debt facilities
Line of Credit Facility [Line Items]
Unused capacity under international debt facilities			$ 227,000,000