Investment Securities - Amortized Cost, Fair Value and Yield by Maturity Date (Parenthetical) (Detail)	6 Months Ended		12 Months Ended
	Jun. 30, 2021		Dec. 31, 2020
Contractual Maturities of Investment Securities [Abstract]
Federal statutory rate	21.00%
Available for sale securities weighted average maturities	5 years 7 months 6 days	[1]	3 years 4 months 24 days
Debt securities available for sale weighted average yield	1.65%	[1],[2]	1.61%

[1] The weighted-average maturity of total available-for-sale investment securities was 3.4 years at December 31, 2020, with a corresponding weighted-average yield of 1.61 percent.

[2] Weighted-average yields for obligations of state and political subdivisions are presented on a fully-taxable equivalent basis based on a federal income tax rate of 21 percent. Yields on investment securities are computed based on amortized cost balances.