Supplemental Condensed Consolidating Guarantor and Non-Guarantor Financial Information - Condensed Consolidating Statement Of Comprehensive Income (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues	$ 512,098,000	$ 444,715,000	$ 1,009,872,000	$ 891,059,000
Operating expenses
Direct cost of revenues	330,318,000	304,071,000	651,435,000	613,143,000
Selling, general and administrative expenses	117,897,000	108,119,000	230,025,000	215,809,000
Special charges	0	30,074,000	0	30,074,000
Amortization of other intangible assets	2,052,000	2,422,000	4,322,000	4,915,000
Operating expenses	450,267,000	444,686,000	885,782,000	863,941,000
Operating income	61,831,000	29,000	124,090,000	27,118,000
Other income (expense)	(4,109,000)	(4,658,000)	(12,153,000)	(9,854,000)
Income (loss) before income tax provision	57,722,000	(4,629,000)	111,937,000	17,264,000
Income tax provision	14,113,000	527,000	29,383,000	8,404,000
Equity in net earnings of subsidiaries	0	0	0	0
Net income (loss)	43,609,000	(5,156,000)	82,554,000	8,860,000
Other comprehensive loss, net of tax:
Foreign currency translation adjustments, net of tax expense of $0	(23,683,000)	10,174,000	(13,237,000)	17,544,000
Total other comprehensive income (loss), net of tax	(23,683,000)	10,174,000	(13,237,000)	17,544,000
Comprehensive income	19,926,000	5,018,000	69,317,000	26,404,000
Foreign currency translation adjustments, tax expense	0	0	0	0
Eliminations
Revenues	(1,262,000)	(2,130,000)	(3,710,000)	(4,722,000)
Operating expenses
Direct cost of revenues	(1,432,000)	(2,069,000)	(3,770,000)	(4,602,000)
Selling, general and administrative expenses	134,000	(61,000)	24,000	(120,000)
Special charges		0		0
Amortization of other intangible assets	(772,000)	(742,000)	(1,580,000)	(1,461,000)
Operating expenses	(2,070,000)	(2,872,000)	(5,326,000)	(6,183,000)
Operating income	808,000	742,000	1,616,000	1,461,000
Other income (expense)	23,000,000	0	0	0
Income (loss) before income tax provision	23,808,000	742,000	1,616,000	1,461,000
Income tax provision	0	0	0	0
Equity in net earnings of subsidiaries	(93,642,000)	5,512,000	(136,509,000)	(22,897,000)
Net income (loss)	(69,834,000)	6,254,000	(134,893,000)	(21,436,000)
Other comprehensive loss, net of tax:
Foreign currency translation adjustments, net of tax expense of $0	0	0	0	0
Total other comprehensive income (loss), net of tax	0	0	0	0
Comprehensive income	(69,834,000)	6,254,000	(134,893,000)	(21,436,000)
FTI Consulting
Revenues	187,569,000	163,649,000	372,890,000	315,456,000
Operating expenses
Direct cost of revenues	115,751,000	108,445,000	231,211,000	219,703,000
Selling, general and administrative expenses	53,472,000	45,908,000	104,153,000	91,706,000
Special charges		13,592,000		13,592,000
Amortization of other intangible assets	874,000	883,000	1,748,000	1,785,000
Operating expenses	170,097,000	168,828,000	337,112,000	326,786,000
Operating income	17,472,000	(5,179,000)	35,778,000	(11,330,000)
Other income (expense)	(32,179,000)	(5,361,000)	(15,249,000)	(10,613,000)
Income (loss) before income tax provision	(14,707,000)	(10,540,000)	20,529,000	(21,943,000)
Income tax provision	2,547,000	(7,034,000)	6,917,000	(12,617,000)
Equity in net earnings of subsidiaries	60,863,000	(1,650,000)	68,942,000	18,186,000
Net income (loss)	43,609,000	(5,156,000)	82,554,000	8,860,000
Other comprehensive loss, net of tax:
Foreign currency translation adjustments, net of tax expense of $0	0	0	0	0
Total other comprehensive income (loss), net of tax	0	0	0	0
Comprehensive income	43,609,000	(5,156,000)	82,554,000	8,860,000
Guarantor Subsidiaries
Revenues	159,288,000	151,716,000	316,417,000	322,742,000
Operating expenses
Direct cost of revenues	110,665,000	108,388,000	220,063,000	226,174,000
Selling, general and administrative expenses	30,494,000	31,730,000	59,474,000	63,109,000
Special charges		7,306,000		7,306,000
Amortization of other intangible assets	313,000	540,000	727,000	1,080,000
Operating expenses	141,472,000	147,964,000	280,264,000	297,669,000
Operating income	17,816,000	3,752,000	36,153,000	25,073,000
Other income (expense)	(572,000)	(71,000)	(881,000)	(498,000)
Income (loss) before income tax provision	17,244,000	3,681,000	35,272,000	24,575,000
Income tax provision	4,977,000	4,219,000	11,017,000	15,137,000
Equity in net earnings of subsidiaries	32,779,000	(3,862,000)	67,567,000	4,711,000
Net income (loss)	45,046,000	(4,400,000)	91,822,000	14,149,000
Other comprehensive loss, net of tax:
Foreign currency translation adjustments, net of tax expense of $0	0	0	0	0
Total other comprehensive income (loss), net of tax	0	0	0	0
Comprehensive income	45,046,000	(4,400,000)	91,822,000	14,149,000
Non-Guarantor Subsidiaries
Revenues	166,503,000	131,480,000	324,275,000	257,583,000
Operating expenses
Direct cost of revenues	105,334,000	89,307,000	203,931,000	171,868,000
Selling, general and administrative expenses	33,797,000	30,542,000	66,374,000	61,114,000
Special charges		9,176,000		9,176,000
Amortization of other intangible assets	1,637,000	1,741,000	3,427,000	3,511,000
Operating expenses	140,768,000	130,766,000	273,732,000	245,669,000
Operating income	25,735,000	714,000	50,543,000	11,914,000
Other income (expense)	5,642,000	774,000	3,977,000	1,257,000
Income (loss) before income tax provision	31,377,000	1,488,000	54,520,000	13,171,000
Income tax provision	6,589,000	3,342,000	11,449,000	5,884,000
Equity in net earnings of subsidiaries	0	0	0	0
Net income (loss)	24,788,000	(1,854,000)	43,071,000	7,287,000
Other comprehensive loss, net of tax:
Foreign currency translation adjustments, net of tax expense of $0	(23,683,000)	10,174,000	(13,237,000)	17,544,000
Total other comprehensive income (loss), net of tax	(23,683,000)	10,174,000	(13,237,000)	17,544,000
Comprehensive income	$ 1,105,000	$ 8,320,000	$ 29,834,000	$ 24,831,000