CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Current Assets:
Cash and cash equivalents	$ 3,683	$ 6,361	$ 11,257
Restricted cash	916	3,088	1,711
Contract receivables, net	202,246	205,484
Contract assets	230,412	201,832
Prepaid expenses and other assets	28,401	28,055
Income tax receivable	0	2,337
Total Current Assets	465,658	447,157
Property and Equipment, net	74,296	75,948
Other Assets:
Goodwill	1,219,031	1,219,476
Other intangible assets, net	86,613	94,904
Operating lease - right-of-use assets	128,356	132,807
Other assets	43,740	41,480
Total Assets	2,017,694	2,011,772
Current Liabilities:
Current portion of long-term debt	26,000	26,000
Accounts payable	119,285	134,503
Contract liabilities	22,099	21,997
Operating lease liabilities	20,889	20,409
Finance lease liabilities	2,545	2,522
Accrued salaries and benefits	70,176	88,021
Accrued subcontractors and other direct costs	48,707	45,645
Accrued expenses and other current liabilities	82,966	79,129
Total Current Liabilities	392,667	418,226
Long-term Liabilities:
Long-term debt	448,748	404,407
Operating lease liabilities - non-current	170,575	175,460
Finance lease liabilities - non-current	13,227	13,874
Deferred income taxes	21,975	26,175
Other long-term liabilities	54,353	56,045
Total Liabilities	1,101,545	1,094,187
Commitments and Contingencies (Note 13)
Stockholders’ Equity:
Preferred stock, par value $.001; 5,000,000 shares authorized; none issued
Common stock, par value $.001; 70,000,000 shares authorized; 24,110,071 and 23,982,132 shares issued at March 31, 2024 and December 31, 2023, respectively; 18,754,762 and 18,845,521 shares outstanding at March 31, 2024 and December 31, 2023, respectively	24	24
Additional paid-in capital	425,160	421,502
Retained earnings	799,796	775,099
Treasury stock, 5,355,309 and 5,136,611 shares at March 31, 2024 and December 31, 2023 respectively	(297,630)	(267,155)
Accumulated other comprehensive loss	(11,201)	(11,885)
Total Stockholders’ Equity	916,149	917,585	$ 853,211
Total Liabilities and Stockholders’ Equity	$ 2,017,694	$ 2,011,772

Represents accrued subcontractor and other direct costs.

No definition available.

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

- Definition

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).