Employee Benefit Plans - Summary of Activity for the Stock Option Component of the Incentive Plan (Detail)	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Compensation Related Costs [Abstract]
Number of options, Outstanding at beginning of the year | shares	393,625
Number of options, Granted during the year | shares	129,850
Number of options, Assumed in acquisition | shares	220,615
Number of options, Exercised during the year | shares	(7,375)
Number of options, Forfeited or expired during the year | shares	(3,275)
Number of options, Outstanding at end of the year | shares	733,440
Number of options, Exercisable at year end | shares	668,640
Weighted average exercise price per share, Outstanding at beginning of the year | $ / shares	$ 37.15
Weighted average exercise price per share, Granted during the year | $ / shares	38.93
Weighted average exercise price per share, Assumed in acquisition | $ / shares	21.99
Weighted average exercise price per share, Exercised during the year | $ / shares	21.31
Weighted average exercise price per share, Forfeited or expired during the year | $ / shares	38.82
Weighted average exercise price per share, Outstanding at end of the year | $ / shares	33.06
Weighted average exercise price per share, Exercisable at year end | $ / shares	$ 32.49