Supplemental Condensed Consolidating Guarantor and Non-Guarantor Financial Information Condensed Consolidating Statement Of Cash Flows (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities
Net cash provided by (used in) operating activities	$ 24,033	$ 111,575
Investing activities
Payments for acquisition of businesses, net of cash received	(8,929)	(56)
Purchases of property and equipment	(20,021)	(22,855)
Other	74	74
Net cash used in investing activities	(28,876)	(22,837)
Financing activities
Borrowings (repayments) under revolving line of credit, net	95,000	(25,000)
Deposits	3,585	2,806
Purchase and retirement of common stock	(155,285)	(2,903)
Net issuance of common stock under equity compensation plans	(2,354)	18,394
Other	(79)	357
Net cash used in financing activities	(59,133)	(6,346)
Effect of exchange rate changes on cash and cash equivalents	5,779	(6,968)
Net increase (decrease) in cash and cash equivalents	(58,197)	75,424
Cash and cash equivalents, beginning of period	216,158	149,760
Cash and cash equivalents, end of period	157,961	225,184
Reportable Legal Entities | FTI Consulting
Operating activities
Net cash provided by (used in) operating activities	(6,155)	16,670
Investing activities
Payments for acquisition of businesses, net of cash received	(8,929)
Purchases of property and equipment	(5,943)	(2,714)
Other	74	74
Net cash used in investing activities	(14,798)	(2,640)
Financing activities
Borrowings (repayments) under revolving line of credit, net	95,000	(25,000)
Purchase and retirement of common stock	(155,285)	(2,903)
Net issuance of common stock under equity compensation plans	(2,354)	18,394
Other	(79)	930
Intercompany transfers	56,955	45,805
Net cash used in financing activities	(5,763)	37,226
Net increase (decrease) in cash and cash equivalents	(26,716)	51,256
Cash and cash equivalents, beginning of period	47,420	35,211
Cash and cash equivalents, end of period	20,704	86,467
Reportable Legal Entities | Guarantor Subsidiaries
Operating activities
Net cash provided by (used in) operating activities	40,052	70,744
Investing activities
Purchases of property and equipment	(9,762)	(16,145)
Net cash used in investing activities	(9,762)	(16,145)
Financing activities
Other		(573)
Intercompany transfers	(30,287)	(54,030)
Net cash used in financing activities	(30,287)	(54,603)
Net increase (decrease) in cash and cash equivalents	3	(4)
Cash and cash equivalents, beginning of period	156	165
Cash and cash equivalents, end of period	159	161
Reportable Legal Entities | Non-Guarantor Subsidiaries
Operating activities
Net cash provided by (used in) operating activities	(9,864)	24,161
Investing activities
Payments for acquisition of businesses, net of cash received		(56)
Purchases of property and equipment	(4,316)	(3,996)
Net cash used in investing activities	(4,316)	(4,052)
Financing activities
Deposits	3,585	2,806
Intercompany transfers	(26,668)	8,225
Net cash used in financing activities	(23,083)	11,031
Effect of exchange rate changes on cash and cash equivalents	5,779	(6,968)
Net increase (decrease) in cash and cash equivalents	(31,484)	24,172
Cash and cash equivalents, beginning of period	168,582	114,384
Cash and cash equivalents, end of period	$ 137,098	$ 138,556