Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Net sales	$ 278.8	$ 286.1
Cost of sales	210.0	211.3
Gross profit	68.8	74.8
Selling, engineering, general and administrative expenses	40.8	42.2
Acquisition and integration-related expenses	0.2	0.3
Operating income	27.8	32.3
Interest expense	1.1	1.5
Other (income) expense, net	(0.5)	0.2
Income before income taxes	27.2	30.6
Income tax expense	5.0	7.2
Net income	$ 22.2	$ 23.4
Basic earnings per share:
Earnings per share (usd per share)	$ 0.37	$ 0.39
Diluted earnings per share:
Earnings per share (usd per share)	$ 0.36	$ 0.38
Weighted average common shares outstanding:
Basic (shares)	60.6	60.5
Diluted (shares)	61.7	61.7

Acquisition and integration related expenses

No definition available.

Name:	fss_Acquisitionandintegrationrelatedexpenses
Namespace Prefix:	fss_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 924
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856

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 210.5-03.2(a),(d))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227