Held to Maturity Debt Securities - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($) security	Dec. 31, 2018 USD ($) security	Dec. 31, 2017 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity securities at carrying value	$ 428,000,000.0	$ 453,100,000
Investment securities held to maturity	453,629,000	479,425,000
Fair value	467,966,000	479,740,000
Proceeds from the calls	$ 42,696,000	$ 39,534,000	$ 55,720,000
Number of securities in an unrealized loss position | security	35	334
Held-to-maturity Securities
Schedule of Held-to-maturity Securities [Line Items]
Recognized gain on calls of securities held to maturity portfolio	$ 72,000	$ 10,000	60,000
Recognized loss on calls of securities held to maturity portfolio	0	1,000	3,000
Proceeds from the calls	33,900,000	32,000,000.0	$ 32,900,000
Mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Investment securities held to maturity	118,000	187,000
Fair value	$ 122,000	$ 190,000