Derivatives - Summary Information Regarding Derivatives (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2016
Customer interest rate swaps
Classified in Other Assets:
Notional Amount	$ 883,306	$ 473,273
Average Maturity (Years)	9 years 6 months	9 years 10 months 24 days
Weighted Average Fixed Rate	3.80%	4.32%
Fair Value	$ 100,310	$ 25,905
Interest rate	196.00%	193.00%
Classified in Other Liabilities:
Notional Amount		$ 85,796
Average Maturity (Years)		9 years
Weighted Average Fixed Rate		3.51%
Fair  Value		$ (947)
Interest rate		195.00%
3rd Party interest rate swaps
Classified in Other Assets:
Notional Amount		$ 85,796
Average Maturity (Years)		9 years
Weighted Average Fixed Rate		3.51%
Fair Value		$ 947
Interest rate		195.00%
Classified in Other Liabilities:
Notional Amount	$ 883,306	$ 473,273
Average Maturity (Years)	9 years 6 months	9 years 10 months 24 days
Weighted Average Fixed Rate	3.80%	4.32%
Fair  Value	$ (100,310)	$ (25,905)
Interest rate	196.00%	193.00%
Interest rate swap (cash flow hedge) | Interest rate swap (cash flow hedge)
Classified in Other Assets:
Notional Amount		$ 30,000
Average Maturity (Years)		1 year 6 months
Weighted Average Fixed Rate		1.10%
Fair Value		$ 271
Classified in Other Liabilities:
Notional Amount	$ 30,000		$ 30,000
Average Maturity (Years)	1 year
Weighted Average Fixed Rate	1.10%
Fair  Value	$ (258)