Investment Securities - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) security position	Dec. 31, 2019 USD ($) security position	Dec. 31, 2018 USD ($)
Investment Securities [Line Items]
Equity securities	$ 29,378,000	$ 41,410,000
Number of security positions in the securities available for sale portfolio in an unrealized loss position (in security) | position	58	182
Fair value of securities available for sale pledged as collateral	$ 789,000,000.0
Weighted-average remaining expected life of residential mortgage-backed securities available for sale, years	3 years 4 months 24 days
Impairment loss	$ 0	$ 2,900,000
Allowance for credit losses	0
Amortized cost	1,293,506,000	1,558,787,000
Fair Value	$ 1,339,473,000	$ 1,566,801,000
Number of security positions in the securities held to maturity portfolio in an unrealized loss position (in security) | security	13	82
Fair value of investments held to maturity pledged as collateral	$ 1,400,000,000
Weighted-average remaining expected life of residential mortgage-backed securities held to maturity, years	4 years 2 months 12 days
Held-to-maturity, allowance for credit loss	$ 1,428,000
Provision for credit losses for held to maturity securities	635,000	$ 0	$ 0
Held-to-maturity, charge-offs	0
US states and political subdivisions debt securities, special revenue bonds, impaired securities
Investment Securities [Line Items]
Amortized cost	680,000
Fair Value	$ 815,000