Stock-Based Compensation - Summary of Non-Vested Stock Option Awards (Detail) - $ / shares shares in Thousands	12 Months Ended
	May 31, 2021	May 31, 2020	May 31, 2019
Number of Stock Options
Non-vested, beginning of year	185
Granted	116	101	96
Vested	(76)
Forfeited	(12)
Non-vested, end of year	213	185
Weighted Average Grant Date Fair Value Per Share
Non-vested, beginning of year	$ 11.06
Granted	10.43
Vested	12.50
Forfeited	9.58
Non-vested, end of year	$ 10.29	$ 11.06