Reconciliations of Equity - Reconciliations of Total Equity (Parenthetical) (Detail) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Number of shares of common stock issued under stock option plan	3,933	4,423	6,680	43,129
Number of common stock shares purchased	71,555	69,736	160,780	70,636
Common stock	$ 0.28	$ 0.25	$ 0.56	$ 0.50
Common Stock [Member]
Number of shares of common stock issued under stock option plan	3,933	4,423	6,680	43,129
Additional Paid-in Capital [Member]
Number of shares of common stock issued under stock option plan	3,933	4,423	6,680	43,129
Treasury Stock [Member]
Number of common stock shares purchased	71,555	69,736	160,780	70,636
Retained Earnings [Member]
Common stock	$ 0.28	$ 0.25	$ 0.56	$ 0.50