Basic and Diluted Earnings per Common Share Attributable to Common Stockholders (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Earnings Per Share Disclosure [Line Items]
Net income attributable to Korn/Ferry International	$ 36,331	$ 30,152	$ 65,372	$ 33,360
Less: distributed and undistributed earnings to nonvested restricted stockholders	402	270	686	283
Basic net earnings attributable to common stockholders	35,929	29,882	64,686	33,077
Add: undistributed earnings to nonvested restricted stockholders	340	220	568	188
Less: reallocation of undistributed earnings to nonvested restricted stockholders	336	218	561	186
Diluted net earnings attributable to common stockholders	$ 35,933	$ 29,884	$ 64,693	$ 33,079
Basic weighted-average number of common shares outstanding	55,390	56,614	55,592	56,401
Diluted weighted-average number of common shares outstanding	55,978	56,983	56,252	56,863
Basic earnings per share	$ 0.65	$ 0.53	$ 1.16	$ 0.59
Diluted earnings per share	$ 0.64	$ 0.52	$ 1.15	$ 0.58
ESPP
Earnings Per Share Disclosure [Line Items]
Stock	1	16	7	27
Restricted Stock
Earnings Per Share Disclosure [Line Items]
Stock	585	335	645	409
Stock Options
Earnings Per Share Disclosure [Line Items]
Stock	2	18	8	26