Legal Matters and Contingencies (Details) $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2023 claim site	Dec. 31, 2023 USD ($) claim site	Dec. 31, 2022 USD ($) claim	Dec. 31, 2021 USD ($) claim
Liability for Asbestos and Environmental Claims, Net [Roll Forward]
Beginning claims		8,139	8,712	8,366
New claims	2,470		2,454	2,482
Resolved claims	(2,545)		(2,204)	(2,211)
Other	172		(823)	75
Ending claims	8,236	8,236	8,139	8,712
Litigation Settlement, Expense \| $		$ 22.1	$ 14.8	$ 10.0
Payments For (Proceeds From) Insurance Settlements \| $		$ (18.4)	$ 4.2	$ (4.7)
Number of former public waste disposal sites \| site	4	4

Loss Contingency, Claims Other, number

No definition available.

Name:	fls_LossContingencyClaimsOtherNumber
Namespace Prefix:	fls_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of former public waste disposal sites.

+ References

No definition available.

+ Details

Name:	fls_NumberOfFormerPublicWasteDisposalSites
Namespace Prefix:	fls_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Payments For (Proceeds From) Insurance Settlements

+ References

No definition available.

+ Details

Name:	fls_PaymentsForProceedsFromInsuranceSettlements
Namespace Prefix:	fls_
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_LiabilityForAsbestosAndEnvironmentalClaimsNetRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of litigation expense, including but not limited to legal, forensic, accounting, and investigative fees.

+ References

No definition available.

+ Details

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

- Definition

Number of claims settled.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483076/450-20-50-4

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483076/450-20-50-9

+ Details

Name:	us-gaap_LossContingencyClaimsSettledNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The total number of new claims filed pertaining to a loss contingency during the period.

+ References

+ Details

Name:	us-gaap_LossContingencyNewClaimsFiledNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of pending claims pertaining to a loss contingency.

+ References

+ Details

Name:	us-gaap_LossContingencyPendingClaimsNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant