Business Segments - Financial Highlights by Business Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Segment Reporting Information [Line Items]
Total revenue	$ 506,793	$ 455,468	$ 985,155	$ 870,385
Net income attributable to Korn/Ferry International	46,034	36,331	7,423	65,372
Net income attributable to noncontrolling interest	1,283	401	1,302	789
Other loss (income), net	4,600	(3,447)	109	(6,801)
Interest expense, net	4,337	3,624	8,440	7,304
Equity in earnings of unconsolidated subsidiaries, net	(100)	(60)	(129)	(90)
Income tax provision (benefit)	14,833	15,619	(1,277)	27,829
Operating income (loss)	70,987	52,468	15,868	94,403
Depreciation and amortization	11,018	12,447	22,749	24,656
Other (loss) income, net	(4,600)	3,447	(109)	6,801
Equity in earnings of unconsolidated subsidiaries	100	60	129	90
EBITDA	77,505	68,422	38,637	125,950
Restructuring (recoveries) charges, net		(202)		78
Integration/acquisition costs	2,835	2,393	5,942	4,981
Tradename write-offs			106,555
Adjusted EBITDA	80,340	70,613	151,134	131,009
Fee Revenue
Segment Reporting Information [Line Items]
Total revenue	495,205	443,018	960,773	844,272
Operating Segments | Executive Search
Segment Reporting Information [Line Items]
Total revenue	202,016	180,583	400,050	346,390
Operating income (loss)	51,467	35,292	92,345	68,204
Depreciation and amortization	1,539	1,925	3,365	3,729
Other (loss) income, net	(3,889)	466	135	929
Equity in earnings of unconsolidated subsidiaries	100	60	129	90
EBITDA	49,217	37,743	95,974	72,952
Restructuring (recoveries) charges, net		273		313
Adjusted EBITDA	49,217	38,016	95,974	73,265
Operating Segments | Executive Search | North America
Segment Reporting Information [Line Items]
Total revenue	119,322	104,329	235,079	199,534
Operating income (loss)	35,328	23,039	61,842	45,109
Depreciation and amortization	968	984	1,947	1,933
Other (loss) income, net	(4,081)	290	(609)	572
Equity in earnings of unconsolidated subsidiaries	100	60	129	90
EBITDA	32,315	24,373	63,309	47,704
Adjusted EBITDA	32,315	24,373	63,309	47,704
Operating Segments | Executive Search | EMEA
Segment Reporting Information [Line Items]
Total revenue	45,636	42,073	93,385	83,131
Operating income (loss)	7,319	6,345	14,288	13,020
Depreciation and amortization	95	459	465	887
Other (loss) income, net	22	43	362	99
EBITDA	7,436	6,847	15,115	14,006
Adjusted EBITDA	7,436	6,847	15,115	14,006
Operating Segments | Executive Search | Asia Pacific
Segment Reporting Information [Line Items]
Total revenue	28,146	26,187	54,771	48,067
Operating income (loss)	6,767	4,381	13,408	7,522
Depreciation and amortization	375	371	745	691
Other (loss) income, net	77	94	252	199
EBITDA	7,219	4,846	14,405	8,412
Restructuring (recoveries) charges, net		273		313
Adjusted EBITDA	7,219	5,119	14,405	8,725
Operating Segments | Executive Search | Latin America
Segment Reporting Information [Line Items]
Total revenue	8,912	7,994	16,815	15,658
Operating income (loss)	2,053	1,527	2,807	2,553
Depreciation and amortization	101	111	208	218
Other (loss) income, net	93	39	130	59
EBITDA	2,247	1,677	3,145	2,830
Adjusted EBITDA	2,247	1,677	3,145	2,830
Operating Segments | Advisory
Segment Reporting Information [Line Items]
Total revenue	221,419	203,836	421,566	387,132
Operating income (loss)	29,426	26,347	(53,653)	45,402
Depreciation and amortization	6,964	8,143	14,395	16,228
Other (loss) income, net	265	455	835	886
EBITDA	36,655	34,945	(38,423)	62,516
Restructuring (recoveries) charges, net		(481)		(241)
Integration/acquisition costs	2,755	2,313	5,782	4,862
Tradename write-offs			106,555
Adjusted EBITDA	39,410	36,777	73,914	67,137
Operating Segments | RPO & Professional Search
Segment Reporting Information [Line Items]
Total revenue	83,358	71,049	163,539	136,863
Operating income (loss)	12,516	9,418	24,161	17,663
Depreciation and amortization	761	784	1,522	1,580
Other (loss) income, net	(79)		26	8
EBITDA	13,198	10,202	25,709	19,251
Restructuring (recoveries) charges, net		6		6
Adjusted EBITDA	13,198	10,208	25,709	19,257
Operating Segments | Fee Revenue | Executive Search
Segment Reporting Information [Line Items]
Total revenue	197,634	176,766	390,558	337,957
Operating Segments | Fee Revenue | Executive Search | North America
Segment Reporting Information [Line Items]
Total revenue	115,863	101,544	227,960	193,377
Operating Segments | Fee Revenue | Executive Search | EMEA
Segment Reporting Information [Line Items]
Total revenue	44,928	41,346	91,582	81,467
Operating Segments | Fee Revenue | Executive Search | Asia Pacific
Segment Reporting Information [Line Items]
Total revenue	27,936	25,912	54,231	47,490
Operating Segments | Fee Revenue | Executive Search | Latin America
Segment Reporting Information [Line Items]
Total revenue	8,907	7,964	16,785	15,623
Operating Segments | Fee Revenue | Advisory
Segment Reporting Information [Line Items]
Total revenue	217,089	199,953	412,464	379,406
Operating Segments | Fee Revenue | RPO & Professional Search
Segment Reporting Information [Line Items]
Total revenue	80,482	66,299	157,751	126,909
Corporate
Segment Reporting Information [Line Items]
Operating income (loss)	(22,422)	(18,589)	(46,985)	(36,866)
Depreciation and amortization	1,754	1,595	3,467	3,119
Other (loss) income, net	(897)	2,526	(1,105)	4,978
EBITDA	(21,565)	(14,468)	(44,623)	(28,769)
Integration/acquisition costs	80	80	160	119
Adjusted EBITDA	$ (21,485)	$ (14,388)	$ (44,463)	$ (28,650)