Restricted Stock Units Issued (Detail) - Restricted Stock Units (RSUs) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Restricted Stock Units
Beginning Restricted Stock Units	43,192	70,364
Restricted Stock Units Granted	4,519	3,743
Dividend Equivalents Earned	1,471	1,507
Restricted Stock Units Settled		(32,422)
Ending Restricted Stock Units	49,182	43,192
Weighted-Average Stock Price
Beginning Restricted Stock Units	$ 41.34	$ 41.20
Restricted Stock Units Granted	43.35	39.26
Dividend Equivalents Earned	46.34	47.34
Restricted Stock Units Settled		41.09
Ending Restricted Stock Units	$ 41.67	$ 41.34