Regulatory Matters - Additional Information (Detail)	Dec. 31, 2019	Sep. 30, 2017	Dec. 31, 2016
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Increase in risk-based capital ratios		0.625%
Forecast [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Minimum capital level requirements	10.50%
Minimum capital level requirements, Tier 1 capital ratio	8.50%
Forecast [Member] | Common Stock [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Minimum capital level requirements, Tier 1 capital ratio	7.00%
Basel III Phase-in Schedule [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Minimum capital level requirements		1.25%	0.625%