Segment Information - Segment Financial Information (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Total sales	$ 1,929.9	$ 1,593.6
Income (loss) from operations	217.3	67.3
Interest expense and other, net	(68.1)	(52.8)
Income (loss) from operations before income taxes	149.2	14.5
Freight Segment
Segment Reporting Information [Line Items]
Total sales	1,301.0	915.5
Transit Segment
Segment Reporting Information [Line Items]
Total sales	628.9	678.1
Operating Segments \| Freight Segment
Segment Reporting Information [Line Items]
Total sales	1,313.5	931.2
Income (loss) from operations	161.7	80.9
Interest expense and other, net	0.0	0.0
Income (loss) from operations before income taxes	161.7	80.9
Operating Segments \| Transit Segment
Segment Reporting Information [Line Items]
Total sales	638.0	682.2
Income (loss) from operations	68.6	59.9
Interest expense and other, net	0.0	0.0
Income (loss) from operations before income taxes	68.6	59.9
Corporate Activities and Elimination
Segment Reporting Information [Line Items]
Total sales	(21.6)	(19.8)
Income (loss) from operations	(13.0)	(73.5)
Interest expense and other, net	(68.1)	(52.8)
Income (loss) from operations before income taxes	(81.1)	(126.3)
Corporate Activities and Elimination \| Freight Segment
Segment Reporting Information [Line Items]
Total sales	12.5	15.7
Corporate Activities and Elimination \| Transit Segment
Segment Reporting Information [Line Items]
Total sales	$ 9.1	$ 4.1

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=68072869&loc=d3e41242-110953

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(10))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(8))
-URI http://asc.fasb.org/extlink&oid=116637232&loc=SL114874131-224263

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(15))
-URI http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260

+ Details

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

- Definition

The net result for the period of deducting operating expenses from operating revenues.

+ References

No definition available.

+ Details

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

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

+ Details

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

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

- Definition

Amount of interest expense and other revenue and expenses that are associated with the entity's normal revenue producing operation.

+ References

No definition available.

+ Details

Name:	wab_InterestExpenseAndOtherNet
Namespace Prefix:	wab_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=wab_FreightSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=wab_TransitSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidationItemsAxis=us-gaap_OperatingSegmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidationItemsAxis=wab_CorporateAndEliminationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: