Loans and Allowance for Loan Losses (Details)	12 Months Ended
Dec. 31, 2018 USD ($) loan	Dec. 31, 2017 USD ($) loan	Dec. 31, 2016 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, gross	$ 11,720,000,000	$ 10,780,000,000
Impaired loans	39,800,000	43,900,000
Impaired loans, related allowance	684,000	338,000
Interest income recognized	1,400,000	1,800,000	$ 1,600,000
Average recorded investment	$ 43,900,000	$ 50,800,000	$ 36,000,000
Number of modified loans \| loan	8	16
Total recorded investment on modified loans	$ 3,006,000	$ 11,001,000
Financial impact on date of restructure	$ 402,000	$ 33,000
Number of previously restructured loans paid off \| loan	7	13
Restructured loans paid off	$ 655,000	$ 1,200,000
Specific reserve		26,000
OREO secured by residential estate properties	25,565,000	32,118,000
Risk Ratings 6, 7 and 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Acquired loans	119,000,000	175,600,000
Impaired \| Substandard, Risk Rating 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Basis in acquired loans at acquisition	4,100,000	17,100,000
Impaired \| Risk Ratings 6, 7 and 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Acquired loans	50,400,000	76,300,000
Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans which formal proceedings in process	3,899,000	5,057,000
Real Estate Acquired in Satisfaction of Debt \| Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
OREO secured by residential estate properties	3,530,000	3,828,000
Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, gross	$ 5,966,453,000	$ 4,239,612,000
Number of modified loans \| loan	4	5
Total recorded investment on modified loans	$ 552,000	$ 8,310,000
Financial impact on date of restructure	212,000	33,000
Real Estate \| Real Estate Acquired in Satisfaction of Debt
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total recorded investment on modified loans	$ 2,288,000	$ 0
Real Estate \| Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans for which payment default \| loan	2	1
Charge-off of loans	$ 92,400	$ 440,000
Loans transferred to OREO	2,169,300
Real Estate \| Single family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, gross	$ 1,440,443,000	$ 1,094,633,000
Number of modified loans \| loan	1	1
Total recorded investment on modified loans	$ 61,000	$ 139,000
Financial impact on date of restructure	$ 0	$ 0
Number of loans for which payment default \| loan	1	1
Charge-off of loans	$ 26,500

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Financing Receivable, Prior Modifications, Number of Contracts Collected

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The recorded balance, net of any applicable reductions (for example, unamortized accretable yield and other-than-temporary impairments), for loans accounted for as debt securities with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

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Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

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Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

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Carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement.

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