Derivatives - Summary Information Regarding Derivatives (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
3rd Party interest rate swaps
Classified in Other Assets:
Notional Amount	$ 326,734	$ 73,075
Average Maturity (Years)	9 years 3 months 18 days	9 years 6 months
Weighted Average Fixed Rate	3.11%	3.20%
Weighted Average Variable Rate	220.00%	255.00%
Fair Value	$ 14,627	$ 503
Classified in Other Liabilities:
Notional Amount	$ 699,190	$ 907,069
Average Maturity (Years)	8 years 4 months 24 days	8 years 8 months 12 days
Weighted Average Fixed Rate	4.02%	3.79%
Weighted Average Variable Rate	196.00%	199.00%
Fair  Value	$ (38,098)	$ (80,231)
Customer interest rate swaps
Classified in Other Assets:
Notional Amount	$ 699,190	$ 907,069
Average Maturity (Years)	8 years 4 months 24 days	8 years 8 months 12 days
Weighted Average Fixed Rate	4.02%	3.79%
Weighted Average Variable Rate	196.00%	199.00%
Fair Value	$ 38,098	$ 80,231
Classified in Other Liabilities:
Notional Amount	$ 326,734	$ 73,075
Average Maturity (Years)	9 years 3 months 18 days	9 years 6 months
Weighted Average Fixed Rate	3.11%	3.20%
Weighted Average Variable Rate	220.00%	255.00%
Fair  Value	$ (14,627)	$ (503)
Interest rate swap (cash flow hedge)
Classified in Other Liabilities:
Notional Amount	$ 30,000	$ 30,000
Average Maturity (Years)	3 months 18 days	6 months
Weighted Average Fixed Rate	1.10%	1.10%
Fair  Value	$ (76)	$ (143)