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Increase Decrease In Capital To Risk Weighted Assets

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Increase Decrease In Common Equity Tier One Capital Ratio

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Increase Decrease In Tier One Risk Based Capital To Risk Weighted Assets

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Nonaccrual status loans contractual past due.

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Number Of Counties Bank Operates

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Number of in store operating branches.

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Number Of Loan Production Offices

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Number Of Locations Acquired

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Number of subsidiary business trust.

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Number of traditional operating branches.

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Significant Of Accounting Policies [Line Items]

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TDR loans payment period in non accrual status.

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The total amount of proceeds received for the sale of securities, categorized neither as held-to-maturity nor trading securities, during the reporting period.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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This element represents the aggregate cost of investments accounted for under the equity method of accounting.

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The difference between the carrying value and the sale price of an investment. A gain would be recognized when the sale price of the investment is greater than the carrying value of the investment. This element refers to the Gain included in earnings and not to the cash proceeds of the sale.

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No definition available.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount of cumulative effect of the change in accounting principle or new accounting pronouncement on retained earnings or other components of equity or net assets in the statement of financial position as of the beginning of the earliest period presented.

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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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The amount of other than temporary impairment (OTTI) losses on equity securities, OTTI related to credit losses on debt securities, and OTTI losses on debt securities when the entity intends to sell the securities or it is more likely than not that the entity will be required to sell the securities before recovery of its amortized cost basis. Additionally, this item includes OTTI losses recognized during the period on investments accounted for under the cost method of accounting.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended	12 Months Ended
	Sep. 30, 2017 USD ($)	Dec. 31, 2018	Dec. 31, 2017 USD ($) Office Segment Location Trust Branch Business	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jan. 01, 2018 USD ($)
Significant Of Accounting Policies [Line Items]
Number of subsidiary business trusts \| Trust			5
Number of loan production offices \| Office			2
Company's investments in the trusts			$ 1,721,000
Number of business segment \| Segment			1
Trading securities			$ 0	$ 0
Sale of classified investment securities			24,796,000	0
Proceeds from sale of investment securities			25,757,000
Gain from sale of classified investment securities			961,000		$ 0
Recognized OTTI losses			$ 0	0
Loans contractual past due			90 days
TDR loans payment period in nonaccrual status			6 months
Recognition of excess tax benefits			$ 109,000	$ 244,000	$ 380,000
Federal statutory income tax rate			35.00%	35.00%	35.00%
Scenario, Forecast [Member]
Significant Of Accounting Policies [Line Items]
Federal statutory income tax rate		21.00%
Tri Counties Bank [Member]
Significant Of Accounting Policies [Line Items]
Number of locations acquired \| Location			3
Number of traditional operating branches \| Branch			57
Number of in-store operating branches \| Branch			9
California [Member]
Significant Of Accounting Policies [Line Items]
Number of counties \| Business			26
ASU 2016-09 [Member]
Significant Of Accounting Policies [Line Items]
Recognition of excess tax benefits			$ 906,000
ASU 2018-02 [Member] \| Subsequent Event [Member] \| Retained Earnings [Member]
Significant Of Accounting Policies [Line Items]
Cumulative-effect adjustment to balance sheet						$ 1,093,000
ASU 2018-02 [Member] \| Subsequent Event [Member] \| Accumulated Other Comprehensive Income (Loss) [Member]
Significant Of Accounting Policies [Line Items]
Cumulative-effect adjustment to balance sheet						$ (1,093,000)
Reclassifications [Member] \| Mortgage Loans on Real Estate [Member] \| Residential 1-4 Family [Member]
Significant Of Accounting Policies [Line Items]
Loans	$ 60,957,000
Reclassifications [Member] \| Consumer [Member] \| Home Equity Loans [Member]
Significant Of Accounting Policies [Line Items]
Loans	$ 5,620,000
Minimum [Member] \| Parent [Member] \| Reclassifications [Member]
Significant Of Accounting Policies [Line Items]
Total risk based capital ratios, increase percentage	0.10%
Tier 1 capital ratios, increase percentage	0.10%
Tier 1 common equity ratios, increase percentage	0.10%
Minimum [Member] \| Tri Countries Bank [Member] \| Reclassifications [Member]
Significant Of Accounting Policies [Line Items]
Total risk based capital ratios, increase percentage	0.10%
Tier 1 capital ratios, increase percentage	0.10%
Tier 1 common equity ratios, increase percentage	0.10%
Maximum [Member] \| Parent [Member] \| Reclassifications [Member]
Significant Of Accounting Policies [Line Items]
Total risk based capital ratios, increase percentage	0.20%
Tier 1 capital ratios, increase percentage	0.20%
Tier 1 common equity ratios, increase percentage	0.20%
Maximum [Member] \| Tri Countries Bank [Member] \| Reclassifications [Member]
Significant Of Accounting Policies [Line Items]
Total risk based capital ratios, increase percentage	0.20%
Tier 1 capital ratios, increase percentage	0.20%
Tier 1 common equity ratios, increase percentage	0.20%
Furniture and Equipment [Member] \| Minimum [Member]
Significant Of Accounting Policies [Line Items]
Estimated useful lives of the related assets or lease terms			3 years
Furniture and Equipment [Member] \| Maximum [Member]
Significant Of Accounting Policies [Line Items]
Estimated useful lives of the related assets or lease terms			10 years
Land Improvements and Buildings [Member] \| Minimum [Member]
Significant Of Accounting Policies [Line Items]
Estimated useful lives of the related assets or lease terms			15 years
Land Improvements and Buildings [Member] \| Maximum [Member]
Significant Of Accounting Policies [Line Items]
Estimated useful lives of the related assets or lease terms			40 years