Business Segments - Financial Highlights by Business Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2018	Jul. 31, 2017
Segment Reporting Information [Line Items]
Total revenue	$ 478,362	$ 414,917
Net (loss) income attributable to Korn/Ferry International	(38,611)	29,041
Net income attributable to noncontrolling interest	19	388
Other income, net	(4,491)	(3,354)
Interest expense, net	4,103	3,680
Equity in earnings of unconsolidated subsidiaries, net	(29)	(30)
Income tax (benefit) provision	(16,110)	12,210
Operating (loss) income	(55,119)	41,935
Depreciation and amortization	11,731	12,209
Other income (loss), net	4,491	3,354
Equity in earnings of unconsolidated subsidiaries, net	29	30
EBITDA	(38,868)	57,528
Restructuring charges, net		280
Integration/acquisition costs	3,107	2,588
Tradename write-offs	106,555
Adjusted EBITDA	70,794	60,396
Fee Revenue
Segment Reporting Information [Line Items]
Total revenue	465,568	401,254
Operating Segments | Executive Search
Segment Reporting Information [Line Items]
Total revenue	198,034	165,807
Operating (loss) income	40,878	32,912
Depreciation and amortization	1,826	1,804
Other income (loss), net	4,024	463
Equity in earnings of unconsolidated subsidiaries, net	29	30
EBITDA	46,757	35,209
Restructuring charges, net		40
Adjusted EBITDA	46,757	35,249
Operating Segments | Executive Search | North America
Segment Reporting Information [Line Items]
Total revenue	115,757	95,205
Operating (loss) income	26,514	22,070
Depreciation and amortization	979	949
Other income (loss), net	3,472	282
Equity in earnings of unconsolidated subsidiaries, net	29	30
EBITDA	30,994	23,331
Adjusted EBITDA	30,994	23,331
Operating Segments | Executive Search | EMEA
Segment Reporting Information [Line Items]
Total revenue	47,749	41,058
Operating (loss) income	6,969	6,675
Depreciation and amortization	370	428
Other income (loss), net	340	56
EBITDA	7,679	7,159
Adjusted EBITDA	7,679	7,159
Operating Segments | Executive Search | Asia Pacific
Segment Reporting Information [Line Items]
Total revenue	26,625	21,880
Operating (loss) income	6,641	3,141
Depreciation and amortization	370	320
Other income (loss), net	175	105
EBITDA	7,186	3,566
Restructuring charges, net		40
Adjusted EBITDA	7,186	3,606
Operating Segments | Executive Search | Latin America
Segment Reporting Information [Line Items]
Total revenue	7,903	7,664
Operating (loss) income	754	1,026
Depreciation and amortization	107	107
Other income (loss), net	37	20
EBITDA	898	1,153
Adjusted EBITDA	898	1,153
Operating Segments | Advisory
Segment Reporting Information [Line Items]
Total revenue	200,147	183,296
Operating (loss) income	(83,079)	19,055
Depreciation and amortization	7,431	8,085
Other income (loss), net	570	431
EBITDA	(75,078)	27,571
Restructuring charges, net		240
Integration/acquisition costs	3,027	2,549
Tradename write-offs	106,555
Adjusted EBITDA	34,504	30,360
Operating Segments | RPO & Professional Search
Segment Reporting Information [Line Items]
Total revenue	80,181	65,814
Operating (loss) income	11,645	8,245
Depreciation and amortization	761	796
Other income (loss), net	105	8
EBITDA	12,511	9,049
Adjusted EBITDA	12,511	9,049
Operating Segments | Fee Revenue | Executive Search
Segment Reporting Information [Line Items]
Total revenue	192,924	161,191
Operating Segments | Fee Revenue | Executive Search | North America
Segment Reporting Information [Line Items]
Total revenue	112,097	91,833
Operating Segments | Fee Revenue | Executive Search | EMEA
Segment Reporting Information [Line Items]
Total revenue	46,654	40,121
Operating Segments | Fee Revenue | Executive Search | Asia Pacific
Segment Reporting Information [Line Items]
Total revenue	26,295	21,578
Operating Segments | Fee Revenue | Executive Search | Latin America
Segment Reporting Information [Line Items]
Total revenue	7,878	7,659
Operating Segments | Fee Revenue | Advisory
Segment Reporting Information [Line Items]
Total revenue	195,375	179,453
Operating Segments | Fee Revenue | RPO & Professional Search
Segment Reporting Information [Line Items]
Total revenue	77,269	60,610
Corporate
Segment Reporting Information [Line Items]
Operating (loss) income	(24,563)	(18,277)
Depreciation and amortization	1,713	1,524
Other income (loss), net	(208)	2,452
EBITDA	(23,058)	(14,301)
Integration/acquisition costs	80	39
Adjusted EBITDA	$ (22,978)	$ (14,262)