Subsequent Events - Debt Refinancing (Details) - 2019 Credit Agreement $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Revolving Credit Facility
Subsequent Event [Line Items]
Credit facility maximum borrowings	$ 500	$ 500
Credit facility potential additional borrowings	$ 250	$ 250
Guaranteed percentage of outstanding voting capital stock	65.00%
Maximum covenant leverage ratio	3.25	3.25
Letter of Credit
Subsequent Event [Line Items]
Credit facility maximum borrowings	$ 75	$ 75
Non-U.S. \| Revolving Credit Facility
Subsequent Event [Line Items]
Credit facility maximum borrowings	200	$ 200
Minimum
Subsequent Event [Line Items]
Line of credit facility, unused capacity, commitment fee percentage		0.10%
Minimum \| Revolving Credit Facility
Subsequent Event [Line Items]
Line of credit facility, covenants holiday, permitted acquisition consideration	75
Minimum \| Base Rate
Subsequent Event [Line Items]
Base rate borrowings margin range		0.00%
Minimum \| LIBOR
Subsequent Event [Line Items]
Base rate borrowings margin range		1.00%
Maximum
Subsequent Event [Line Items]
Line of credit facility, unused capacity, commitment fee percentage		0.25%
Maximum \| Revolving Credit Facility
Subsequent Event [Line Items]
Line of credit facility, permitted dividends and stock repurchases	35
Line of credit facility, covenants, permitted other incremental cash payments	$ 50
Maximum \| Base Rate
Subsequent Event [Line Items]
Base rate borrowings margin range		0.75%
Maximum \| LIBOR
Subsequent Event [Line Items]
Base rate borrowings margin range		1.75%

Percentage of outstanding voting capital stock provided as a guarantee of obligations.

No definition available.

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Period Type:	duration

- Definition

Line Of Credit Facility Covenant Terms Leverage Ratio Maximum

+ References

No definition available.

+ Details

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- Definition

Permitted acquisition consideration amount which would allow for a temporary covenant holiday period.

+ References

No definition available.

+ Details

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Namespace Prefix:	fss_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of dividends and stock repurchases the Company is permitted to fund if its leverage ratio is greater than what is defined in the covenant.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Amount of other incremental cash payments the Company is permitted to make if its leverage ratio is greater than what is defined in the covenant.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Line of Credit Facility, Maximum Borrowing Capacity, Available Increment

+ References

No definition available.

+ Details

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Namespace Prefix:	fss_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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- 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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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Period Type:	duration

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ 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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