Basis of Presentation and Nature of Operations (Policies)	3 Months Ended
Mar. 31, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements include the accounts of ICF International, Inc. (“ICFI”) and its principal subsidiary, ICF Consulting Group, Inc. (“Consulting,” and together with ICFI, the “Company”), and have been prepared in accordance with United States (“U.S.”) generally accepted accounting principles (“U.S. GAAP”). Consulting is a wholly owned subsidiary of ICFI. ICFI is a holding company with no operations or assets other than its investment in the common stock of Consulting. All other subsidiaries of the Company are wholly owned by Consulting. All significant intercompany transactions and balances have been eliminated.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent liabilities at the date of the consolidated financial statements, and the reported amounts of revenue and expenses during the reporting periods. Areas of the consolidated financial statements where estimates may have the most significant effect include contractual and regulatory reserves, valuation and lives of tangible and intangible assets, contingent consideration related to business acquisitions, impairment of goodwill and long-lived assets, accrued liabilities, revenue recognition and costs to complete fixed-price contracts, bonus and other incentive compensation, stock-based compensation, reserves for tax benefits and valuation allowances on deferred tax assets, provisions for income taxes, collectability of receivables, and loss accruals for litigation. Actual results experienced by the Company may differ from management's estimates.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recent Accounting Pronouncements Not Yet Adopted Reference Rate Reform In March 2020, the Financial Accounting Standards Board issued Accounting Standards Update (“ASU”) 2020-04, Facilitation of the Effects of Reference Rate Reform on Financial Reporting. The standard is intended to provide temporary optional expedients and exceptions to the U.S. GAAP guidance on contract modifications and hedge accounting to ease the financial reporting burdens related to the expected market transition from the London Interbank Offered Rate (“LIBOR”) and other interbank offered rates to alternative reference rates. The provisions of this ASU are elective and apply to all entities, subject to meeting certain criteria, that have debt or hedging contracts, among other contracts, that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. The Company can elect to not apply certain modification accounting requirements to contracts affected by reference rate reform if certain criteria are met. Also, the Company can elect various optional expedients that would allow it to continue to apply hedge accounting for hedging relationships affected by reference rate reform if certain criteria are met. This guidance was effective beginning on March 12, 2020, and the Company may elect to apply the amendments prospectively through December 31, 2022. The Company is currently evaluating the impact of the transition from LIBOR to alternative reference interest rates for the current Credit Facility (see Note 7—Long-Term Debt) and the related interest rate hedges (see Note 9—Derivative Instruments and Hedging Activities) but does not expect a significant impact to its operating results, financial position, or cash flows.

Basis of Presentation and Nature of Operations (Policies)

3 Months Ended

Mar. 31, 2022

The accompanying consolidated financial statements include the accounts of ICF International, Inc. (“ICFI”) and its principal subsidiary, ICF Consulting Group, Inc. (“Consulting,” and together with ICFI, the “Company”), and have been prepared in accordance with United States (“U.S.”) generally accepted accounting principles (“U.S. GAAP”). Consulting is a wholly owned subsidiary of ICFI. ICFI is a holding company with no operations or assets other than its investment in the common stock of Consulting. All other subsidiaries of the Company are wholly owned by Consulting. All significant intercompany transactions and balances have been eliminated.

Use of Estimates

The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent liabilities at the date of the consolidated financial statements, and the reported amounts of revenue and expenses during the reporting periods. Areas of the consolidated financial statements where estimates may have the most significant effect include contractual and regulatory reserves, valuation and lives of tangible and intangible assets, contingent consideration related to business acquisitions, impairment of goodwill and long-lived assets, accrued liabilities, revenue recognition and costs to complete fixed-price contracts, bonus and other incentive compensation, stock-based compensation, reserves for tax benefits and valuation allowances on deferred tax assets, provisions for income taxes, collectability of receivables, and loss accruals for litigation. Actual results experienced by the Company may differ from management's estimates.

Recent Accounting Pronouncements

Recent Accounting Pronouncements Not Yet Adopted

Reference Rate Reform

In March 2020, the Financial Accounting Standards Board issued Accounting Standards Update (“ASU”) 2020-04, Facilitation of the Effects of Reference Rate Reform on Financial Reporting. The standard is intended to provide temporary optional expedients and exceptions to the U.S. GAAP guidance on contract modifications and hedge accounting to ease the financial reporting burdens related to the expected market transition from the London Interbank Offered Rate (“LIBOR”) and other interbank offered rates to alternative reference rates. The provisions of this ASU are elective and apply to all entities, subject to meeting certain criteria, that have debt or hedging contracts, among other contracts, that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. The Company can elect to not apply certain modification accounting requirements to contracts affected by reference rate reform if certain criteria are met. Also, the Company can elect various optional expedients that would allow it to continue to apply hedge accounting for hedging relationships affected by reference rate reform if certain criteria are met. This guidance was effective beginning on March 12, 2020, and the Company may elect to apply the amendments prospectively through December 31, 2022. The Company is currently evaluating the impact of the transition from LIBOR to alternative reference interest rates for the current Credit Facility (see Note 7—Long-Term Debt) and the related interest rate hedges (see Note 9—Derivative Instruments and Hedging Activities) but does not expect a significant impact to its operating results, financial position, or cash flows.