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Summary of Significant Accounting Policies (Details)			3 Months Ended	12 Months Ended
	Jan. 01, 2020	Oct. 01, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)
Number of insurance-related subsidiaries | item				1
Investment Securities
Number of components in which other-than-temporary impairment is segregated | item				2
Non-Accrual Loans
Period of charge off for past due unsecured consumer loans				90 days
Minimum period that past due unsecured loans outstanding may not be placed on nonaccrual status under special circumstances				90 days
Maximum period of non-consumer loans outstanding that is used to evaluate whether loans should be placed on non-accrual status				90 days
Other Real Estate Owned and Repossessed Assets
Other real estate owned				$ 71,103,000	$ 57,344,000
Repossessed assets				$ 7,137,000	6,454,000
Income Taxes
Percentage of likelihood of realization of recognized tax benefit				50.00%
Liability for unrecognized tax benefits				$ 0	0
Interest expense related to uncertain tax positions				0	0	$ 0
Penalties related to uncertain tax positions				0	$ 0	$ 0
Goodwill and Identified Intangible Assets
Goodwill impairment loss		$ 0
Impairment of identified intangible assets				$ 0
Segments of an Enterprise and Related Information
Number of operating segments | item				1
Number of active operating bank subsidiaries | item				5
New Accounting Standards
One-time reclassification from AOCI to retained earnings, relating to the Tax Cuts and Jobs Act of 2017			$ 5,997,000
Equity securities with readily determinable fair values
New Accounting Standards
Net unrealized loss on available-for-sale equity securities				$ 189,000
ASU 2016-02
New Accounting Standards
Right of use asset							$ 6,400,000
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Lease liability							$ 6,400,000
Lease liability, statement of Financial Position Location							us-gaap:OtherLiabilities
Amortization of the right of use asset				$ 1,019,000
ASU 2016-13 | Minimum | Forecast adjustment
New Accounting Standards
Impact of the increase of allowance for probable loan losses	2.00%
ASU 2016-13 | Maximum | Forecast adjustment
New Accounting Standards
Impact of the increase of allowance for probable loan losses	6.00%

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Amount before tax, after reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss.

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