Reconciliations of Equity - Reconciliations of Total Equity (Parenthetical) (Detail) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Number of shares of common stock issued under stock option plan	40,435	13,256	47,115	56,385
Number of common stock shares purchased on open market		73,821	160,780	144,457
Common stock	$ 0.28	$ 0.25	$ 0.84	$ 0.75
Common Stock [Member]
Number of shares of common stock issued under stock option plan	40,435	13,256	47,115	56,385
Additional Paid-in Capital [Member]
Number of shares of common stock issued under stock option plan	40,435	13,256	47,115	56,385
Treasury Stock [Member]
Number of common stock shares purchased on open market		73,821	160,780	144,457
Retained Earnings [Member]
Common stock	$ 0.28	$ 0.25	$ 0.84	$ 0.75