Summary of Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2021
Accounting Policies [Abstract]
Organization and Description of the Business	Organization and Description of the Business Federal Signal Corporation was founded in 1901 and was reincorporated as a Delaware corporation in 1969. References herein to the “Company,” “we,” “our” or “us” refer collectively to Federal Signal Corporation and its subsidiaries. Products manufactured and services rendered by the Company are divided into two reportable segments: Environmental Solutions Group and Safety and Security Systems Group. The individual operating businesses are organized as such because they share certain characteristics, including technology, marketing, distribution and product application, which create long-term synergies. These segments are discussed in Note 12 – Segment Information.
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying unaudited condensed consolidated financial statements represent the consolidation of Federal Signal Corporation and its subsidiaries included herein and have been prepared by the Company pursuant to the rules and regulations of the United States (“U.S.”) Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) have been condensed or omitted pursuant to such rules and regulations, although the Company believes that the disclosures presented herein are adequate to ensure the information presented is not misleading. Except as otherwise noted, these condensed consolidated financial statements have been prepared in accordance with the Company’s accounting policies described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020, and should be read in conjunction with those consolidated financial statements and the notes thereto. In addition, as discussed in Note 2 – Acquisitions, on February 17, 2021, the Company completed the acquisition of all of the outstanding equity of OSW Equipment & Repair, LLC (“OSW”), a leading manufacturer of dump truck bodies and custom upfitter of truck equipment and trailers. The acquisition also includes OSW’s wholly-owned subsidiaries, Northend Truck Equipment, LLC and Western Truck Body Mfg. ULC. The Condensed Consolidated Balance Sheet as of June 30, 2021 includes preliminary fair values assigned to the assets acquired and liabilities assumed in connection with the acquisition, and the Condensed Consolidated Statements of Operations for the three and six months ended June 30, 2021 include the post-acquisition operating results of OSW. These condensed consolidated financial statements include all normal and recurring adjustments that we considered necessary to present a fair statement of our results of operations, financial condition and cash flow. Intercompany balances and transactions have been eliminated in consolidation. The results reported in these condensed consolidated financial statements should not be regarded as necessarily indicative of results that may be expected for the entire year, which may differ materially due to, among other things, the risk factors described under Part I, Item 1A, Risk Factors, of the Company’s Annual Report on Form 10-K for the year ended December 31, 2020, which was filed with the SEC on February 25, 2021. While we label our quarterly information using a calendar convention whereby our first, second and third quarters are labeled as ending on March 31, June 30 and September 30, respectively, it is our longstanding practice to establish interim quarterly closing dates based on a 13-week period ending on a Saturday, with our fiscal year ending on December 31. The effects of this practice are not material and exist only within a reporting year.
Recent Accounting Pronouncements and Accounting Changes	Recent Accounting Pronouncements and Accounting Changes In December 2019, the Financial Accounting Standards Board issued Accounting Standards Update (“ASU”) No. 2019-12, Income Taxes (Topic 740), Simplifying the Accounting for Income Taxes, which is intended to simplify various aspects related to accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. The amendments in this ASU are effective for fiscal years beginning after December 15, 2020 and interim periods within those fiscal years, with early adoption permitted. The amendments should be applied on a retrospective, modified retrospective or prospective basis, depending on the area covered by the update. The Company adopted this guidance on a prospective basis effective January 1, 2021. The adoption of this ASU did not have a material impact on the Company’s consolidated financial statements. There are no new accounting pronouncements issued, but not yet adopted, that are expected to have a material impact on the Company’s results of operations, financial position or cash flow.
Use of Estimates	Use of EstimatesThe preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect (i) the reported amounts of assets and liabilities, (ii) the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and (iii) the reported amounts of revenues and expenses during the reporting period. Actual results and outcomes may differ, including as a result of the risks and uncertainties associated with the COVID-19 pandemic, including emerging variants, and its effect on the global economy.
Fair Value Measurements	The Company uses a three-level fair value hierarchy that prioritizes the inputs used to measure fair value. This hierarchy maximizes the use of observable inputs and minimizes the use of unobservable inputs. Observable inputs are developed based on market data obtained from independent sources, while unobservable inputs reflect the Company’s assumptions about valuation based on the best information available in the circumstances. The three levels of inputs are classified as follows: •Level 1 — quoted prices in active markets for identical assets or liabilities; •Level 2 — observable inputs, other than quoted prices included in Level 1, such as quoted prices for markets that are not active, or other inputs that are observable or can be corroborated by observable market data; and •Level 3 — unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities, including certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs. In determining fair value, the Company uses various valuation approaches within the fair value measurement framework. The valuation methodologies used for the Company’s assets and liabilities measured at fair value and their classification in the valuation hierarchy are summarized below: Cash Equivalents Cash equivalents primarily consist of time-based deposits and interest-bearing instruments with maturities of three months or less. The Company classified cash equivalents as Level 1 due to the short-term nature of these instruments and measured the fair value based on quoted prices in active markets for identical assets. Interest Rate Swaps As described in Note 5 – Debt, the Company may, from time to time, execute interest rate swaps as a means of fixing the floating interest rate component on a portion of its floating-rate debt. The Company classifies its interest rate swaps as Level 2 due to the use of a discounted cash flow model based on the terms of the contract and the interest rate curve (Level 2 inputs) to calculate the fair value of the swaps. Contingent Consideration The Company has a contingent obligation to pay up to $15.5 million to the former owners of Mark Rite Lines Equipment Company, Inc. (“MRL”), a U.S. manufacturer of truck-mounted and ride-on road-marking and line-removal equipment acquired by the Company on July 1, 2019, if specified financial results are met over future reporting periods (i.e., an earn-out). The contingent earn-out payment, if earned, would be due to be paid following the third anniversary of the closing of the acquisition. Liabilities for contingent consideration are measured at fair value each reporting period, with the acquisition-date fair value included as part of the consideration transferred. Subsequent changes in fair value are included as a component of Acquisition and integration-related expenses on the Condensed Consolidated Statements of Operations. The Company uses an income approach to value the contingent consideration obligation based on the present value of risk-adjusted future cash flows under either a scenario-based or option-pricing method, as appropriate. Due to the lack of relevant observable market data over fair value inputs, such as prospective financial information or probabilities of future events as of June 30, 2021, the Company has classified the contingent consideration liability within Level 3 of the fair value hierarchy outlined in ASC 820, Fair Value Measurements.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2021

Organization and Description of the Business

Federal Signal Corporation was founded in 1901 and was reincorporated as a Delaware corporation in 1969. References herein to the “Company,” “we,” “our” or “us” refer collectively to Federal Signal Corporation and its subsidiaries.

Products manufactured and services rendered by the Company are divided into two reportable segments: Environmental Solutions Group and Safety and Security Systems Group. The individual operating businesses are organized as such because they share certain characteristics, including technology, marketing, distribution and product application, which create long-term synergies. These segments are discussed in Note 12 – Segment Information.

Basis of Presentation and Consolidation

The accompanying unaudited condensed consolidated financial statements represent the consolidation of Federal Signal Corporation and its subsidiaries included herein and have been prepared by the Company pursuant to the rules and regulations of the United States (“U.S.”) Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) have been condensed or omitted pursuant to such rules and regulations, although the Company believes that the disclosures presented herein are adequate to ensure the information presented is not misleading. Except as otherwise noted, these condensed consolidated financial statements have been prepared in accordance with the Company’s accounting policies described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020, and should be read in conjunction with those consolidated financial statements and the notes thereto.

In addition, as discussed in Note 2 – Acquisitions, on February 17, 2021, the Company completed the acquisition of all of the outstanding equity of OSW Equipment & Repair, LLC (“OSW”), a leading manufacturer of dump truck bodies and custom upfitter of truck equipment and trailers. The acquisition also includes OSW’s wholly-owned subsidiaries, Northend Truck Equipment, LLC and Western Truck Body Mfg. ULC. The Condensed Consolidated Balance Sheet as of June 30, 2021 includes preliminary fair values assigned to the assets acquired and liabilities assumed in connection with the acquisition, and the Condensed Consolidated Statements of Operations for the three and six months ended June 30, 2021 include the post-acquisition operating results of OSW.

These condensed consolidated financial statements include all normal and recurring adjustments that we considered necessary to present a fair statement of our results of operations, financial condition and cash flow. Intercompany balances and transactions have been eliminated in consolidation.

The results reported in these condensed consolidated financial statements should not be regarded as necessarily indicative of results that may be expected for the entire year, which may differ materially due to, among other things, the risk factors described under Part I, Item 1A, Risk Factors, of the Company’s Annual Report on Form 10-K for the year ended December 31, 2020, which was filed with the SEC on February 25, 2021. While we label our quarterly information using a calendar convention whereby our first, second and third quarters are labeled as ending on March 31, June 30 and September 30, respectively, it is our longstanding practice to establish interim quarterly closing dates based on a 13-week period ending on a Saturday, with our fiscal year ending on December 31. The effects of this practice are not material and exist only within a reporting year.

Recent Accounting Pronouncements and Accounting Changes

In December 2019, the Financial Accounting Standards Board issued Accounting Standards Update (“ASU”) No. 2019-12, Income Taxes (Topic 740), Simplifying the Accounting for Income Taxes, which is intended to simplify various aspects related to accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. The amendments in this ASU are effective for fiscal years beginning after December 15, 2020 and interim periods within those fiscal years, with early adoption permitted. The amendments should be applied on a retrospective, modified retrospective or prospective basis, depending on the area covered by the update. The Company adopted this guidance on a prospective basis effective January 1, 2021. The adoption of this ASU did not have a material impact on the Company’s consolidated financial statements.

There are no new accounting pronouncements issued, but not yet adopted, that are expected to have a material impact on the Company’s results of operations, financial position or cash flow.

Use of Estimates

Use of EstimatesThe preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect (i) the reported amounts of assets and liabilities, (ii) the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and (iii) the reported amounts of revenues and expenses during the reporting period. Actual results and outcomes may differ, including as a result of the risks and uncertainties associated with the COVID-19 pandemic, including emerging variants, and its effect on the global economy.

Fair Value Measurements

The Company uses a three-level fair value hierarchy that prioritizes the inputs used to measure fair value. This hierarchy maximizes the use of observable inputs and minimizes the use of unobservable inputs. Observable inputs are developed based on market data obtained from independent sources, while unobservable inputs reflect the Company’s assumptions about valuation based on the best information available in the circumstances. The three levels of inputs are classified as follows:

•Level 1 — quoted prices in active markets for identical assets or liabilities;

•Level 2 — observable inputs, other than quoted prices included in Level 1, such as quoted prices for markets that are not active, or other inputs that are observable or can be corroborated by observable market data; and

•Level 3 — unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities, including certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs.

In determining fair value, the Company uses various valuation approaches within the fair value measurement framework. The valuation methodologies used for the Company’s assets and liabilities measured at fair value and their classification in the valuation hierarchy are summarized below:

Cash Equivalents

Cash equivalents primarily consist of time-based deposits and interest-bearing instruments with maturities of three months or less. The Company classified cash equivalents as Level 1 due to the short-term nature of these instruments and measured the fair value based on quoted prices in active markets for identical assets.

Interest Rate Swaps

As described in Note 5 – Debt, the Company may, from time to time, execute interest rate swaps as a means of fixing the floating interest rate component on a portion of its floating-rate debt. The Company classifies its interest rate swaps as Level 2 due to the use of a discounted cash flow model based on the terms of the contract and the interest rate curve (Level 2 inputs) to calculate the fair value of the swaps.

Contingent Consideration

The Company has a contingent obligation to pay up to $15.5 million to the former owners of Mark Rite Lines Equipment Company, Inc. (“MRL”), a U.S. manufacturer of truck-mounted and ride-on road-marking and line-removal equipment acquired by the Company on July 1, 2019, if specified financial results are met over future reporting periods (i.e., an earn-out). The contingent earn-out payment, if earned, would be due to be paid following the third anniversary of the closing of the acquisition. Liabilities for contingent consideration are measured at fair value each reporting period, with the acquisition-date fair value included as part of the consideration transferred. Subsequent changes in fair value are included as a component of Acquisition and integration-related expenses on the Condensed Consolidated Statements of Operations.

The Company uses an income approach to value the contingent consideration obligation based on the present value of risk-adjusted future cash flows under either a scenario-based or option-pricing method, as appropriate. Due to the lack of relevant observable market data over fair value inputs, such as prospective financial information or probabilities of future events as of June 30, 2021, the Company has classified the contingent consideration liability within Level 3 of the fair value hierarchy outlined in ASC 820, Fair Value Measurements.