Stock-Based Compensation - Summary of Non-Vested Stock Option Awards (Detail) - $ / shares shares in Thousands	12 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2018
Number of Stock Options
Non-vested, beginning of year	158
Granted	101	96	90
Vested	(73)
Forfeited	(1)
Non-vested, end of year	185	158
Weighted Average Grant Date Fair Value Per Share
Non-vested, beginning of year	$ 12.26
Granted	10.21
Vested	12.42
Forfeited	15.98
Non-vested, end of year	$ 11.06	$ 12.26