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, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Earnings Per Share Disclosure [Line Items]
Net income attributable to Korn/Ferry International	$ 46,034	$ 36,331	$ 7,423	$ 65,372
Less: distributed and undistributed earnings to nonvested restricted stockholders	485	402	118	686
Basic net earnings attributable to common stockholders	45,549	35,929	7,305	64,686
Add: undistributed earnings to nonvested restricted stockholders	425	340		568
Less: reallocation of undistributed earnings to nonvested restricted stockholders	419	336		561
Diluted net earnings attributable to common stockholders	$ 45,555	$ 35,933	$ 7,305	$ 64,693
Basic weighted-average number of common shares outstanding	55,461	55,390	55,420	55,592
Diluted weighted-average number of common shares outstanding	56,239	55,978	56,306	56,252
Basic earnings per share	$ 0.82	$ 0.65	$ 0.13	$ 1.16
Diluted earnings per share	$ 0.81	$ 0.64	$ 0.13	$ 1.15
ESPP
Earnings Per Share Disclosure [Line Items]
Stock	11	1	14	7
Restricted Stock
Earnings Per Share Disclosure [Line Items]
Stock	767	585	871	645
Stock Options
Earnings Per Share Disclosure [Line Items]
Stock		2	1	8