Business Segment Information - Sales and Operating Results of Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Sales and operating results of reportable segments
Sales	$ 1,684.5	$ 1,642.3
Purchase accounting depreciation and amortization	(10.0)	(4.1)
General corporate – net	(32.8)	(21.9)
Non-operating pension and postretirement benefit (cost) credit	(8.7)	2.6
Gain (loss) on investments	71.0	(246.4)
Valuation adjustments related to the registration of PTC Shares	0.0	33.7
Interest (expense) income - net	(24.0)	(18.0)
Income before income taxes	334.6	120.8
Operating Segments
Sales and operating results of reportable segments
Sales	1,684.5	1,642.3
Segment operating earnings	339.1	374.9
Architecture & Software
Sales and operating results of reportable segments
Sales	751.6	753.1
Architecture & Software \| Operating Segments
Sales and operating results of reportable segments
Sales	751.6	753.1
Segment operating earnings	223.7	237.0
Control Products & Solutions
Sales and operating results of reportable segments
Sales	932.9	889.2
Control Products & Solutions \| Operating Segments
Sales and operating results of reportable segments
Sales	932.9	889.2
Segment operating earnings	$ 115.4	$ 137.9

Equity Securities, FV-NI, Unrealized Gain (Loss), Loss On Investment

No definition available.

Name:	rok_EquitySecuritiesFVNIUnrealizedGainLossLossOnInvestment
Namespace Prefix:	rok_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Equity Securities, FV-NI, Unrealized Gain (Loss), Valuation Adjustment

+ References

No definition available.

+ Details

Name:	rok_EquitySecuritiesFVNIUnrealizedGainLossValuationAdjustment
Namespace Prefix:	rok_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

General Corporate - Net

+ References

No definition available.

+ Details

Name:	rok_GeneralCorporateNet
Namespace Prefix:	rok_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Non-operating pension costs consist of defined benefit plan interest cost, expected return on plan assets, amortization of actuarial gains and losses and the impacts of any plan curtailments or settlements. These costs are excluded from segment operating earnings.

+ References

No definition available.

+ Details

Name:	rok_NonOperatingPensionCost
Namespace Prefix:	rok_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Purchase accounting depreciation and amortization that is not allocated to the segments for the purposes of determining segment operating earnings.

+ References

No definition available.

+ Details

Name:	rok_PurchaseAccountingDepreciationAndAmortization
Namespace Prefix:	rok_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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.

+ References

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

Amount of interest revenue (income derived from investments in debt securities and on cash and cash equivalents) net of interest expense (cost of borrowed funds accounted for as interest).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

+ Details

Name:	us-gaap_InterestRevenueExpenseNet
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

- References

No definition available.

+ Details

Name:	us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
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

- Details

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

- Details

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

- Details

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