Stock-Based Compensation - Schedule of Nonvested Stock Option Outstanding (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares
Nonvested at beginning of period (in shares)	124,348
Granted (in shares)	120,019
Forfeited (in shares)	0
Nonvested at end of period (in shares)	140,076	124,348
Weighted- Average Exercise Price
Nonvested at beginning of period (in dollars per share)	$ 42.76
Granted (in dollars per share)	43.28
Forfeited (in dollars per share)	0
Nonvested at end of period (in dollars per share)	43.91	$ 42.76
Weighted- Average Grant Date Fair Value
Nonvested at beginning of period (in dollars per share)	10.38
Granted (in dollars per share)	10.26	11.62	$ 11.50
Forfeited (in dollars per share)	0
Nonvested at end of period (in dollars per share)	$ 10.53	$ 10.38
Vested (in shares)	104,291
Vested (in dollars per share)	$ 41.80
Vested (in dollars per share)	$ 10.04