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Description of Business and Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Days from origination after which mortgage loan are sold	30 days
Loan upon which a default of principal or interest has existed for a period	90 days
Intangible assets, Estimated useful lives	6 years 8 months 12 days
Accounting Standards Update 2016-01 [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Additional income from changes in equity investments	$ 48,900
Accounting Standards Update 2016-01 [Member] | Other Assets [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Effect of change in accounting principle	5,700,000
Accounting Standards Update 2016-01 [Member] | Equity Securities [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Effect of change in accounting principle	(5,700,000)
Accounting Standards Update 2016-01 [Member] | Retained Earnings [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Effect of change in accounting principle	618,000
Accounting Standards Update 2016-01 [Member] | Accumulated Other Comprehensive Income [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Effect of change in accounting principle	$ 618,000
Accounting Standards Update 2016-02 [Member] | Scenario Forecast [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Effect of change in accounting principle		$ 3,000,000
Core Deposit Intangibles [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Intangible assets, Estimated useful lives	6 years 10 months 24 days
Minimum [Member] | Core Deposit Intangibles [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Intangible assets, Estimated useful lives	7 years
Minimum [Member] | Customer Relationship Intangibles [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Intangible assets, Estimated useful lives	3 years
Maximum [Member] | Core Deposit Intangibles [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Intangible assets, Estimated useful lives	10 years
Maximum [Member] | Customer Relationship Intangibles [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Intangible assets, Estimated useful lives	18 years
Home Equity Lines of Credit [Member] | Maximum [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Loans and finance receivables portfolio percentage	9.00%
First Liens [Member] | Minimum [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Loans and finance receivables portfolio percentage	82.00%
Junior Liens [Member] | Maximum [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Loans and finance receivables portfolio percentage	9.00%

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