Loans and Allowance for Loan Losses (Details)	12 Months Ended
Dec. 31, 2019 USD ($) loan	Dec. 31, 2018 USD ($) loan	Dec. 31, 2017 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, gross	$ 14,430,000,000	$ 11,720,000,000
Impaired loans	68,900,000	35,800,000
Impaired loans, related allowance	5,747,000	684,000
Interest income recognized	1,500,000	1,400,000	$ 1,800,000
Average recorded investment	$ 59,100,000	$ 43,900,000	$ 50,800,000
Number of modified loans \| loan	4	8
Total recorded investment on modified loans	$ 997,000	$ 3,006,000
Financial impact on date of restructure	$ 0	$ 402,000
Number of previously restructured loans paid off \| loan	3	7
Restructured loans paid off	$ 81,600	$ 655,000
OREO secured by residential estate properties	19,121,000	25,565,000
Risk Ratings 6, 7 and 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Acquired loans	209,800,000	119,000,000.0
Impaired \| Substandard, Risk Rating 6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Basis in acquired loans at acquisition	13,400,000	4,100,000
Impaired \| Risk Ratings 6, 7 and 8
Accounts, Notes, Loans and Financing Receivable [Line Items]
Acquired loans	103,100,000	50,400,000
Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans which formal proceedings in process	5,789,000	3,899,000
Real Estate Acquired in Satisfaction of Debt \| Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
OREO secured by residential estate properties	4,458,000	3,530,000
Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases receivable, gross	$ 6,884,422,000	$ 5,966,453,000
Number of modified loans \| loan	4	4
Total recorded investment on modified loans	$ 997,000	$ 552,000
Financial impact on date of restructure	0	212,000
Real Estate \| Real Estate Acquired in Satisfaction of Debt
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total recorded investment on modified loans	$ 0	$ 2,288,000
Real Estate \| Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans for which payment default \| loan	4	2
Charge-off of loans	$ 552,000	$ 92,400
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	$ 1,444,620,000	$ 1,440,443,000
Number of modified loans \| loan	4	1
Total recorded investment on modified loans	$ 997,000	$ 61,000
Financial impact on date of restructure	$ 0	$ 0
Number of loans for which payment default \| loan		1
Charge-off of loans		$ 26,500

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