Nature of Operations and Summary of Significant Accounting Policies (Details Textual)	12 Months Ended
	Dec. 31, 2018 USD ($) quarter step reporting_unit division operating_segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Number of Bank Divisions | division	14
Number of Operating Segments | operating_segment	1
Maximum Period of Original Maturity to be Included in Cash and Cash Equivalents	3 months
Federal Reserve Balance or Cash on Hand Required	$ 53,626,000
Minimum Period Past Due to Consider Loans as Delinquent	30 days
Minimum Period Past Due to Consider Loans as Non Accrual	90 days
Number of Quarters Used to Evaluate Historical Loss Experience | quarter	12
Maximum period up to which purchase price of business is allocated to assets acquired and liabilities assumed	1 year
Number of Reporting Units Subsequent to Aggregation for Goodwill Assessment | reporting_unit	1
Number of steps included in goodwill impairment test | step	2
Revenue from Contracts with Customers	$ 76,664,000	$ 69,808,000	$ 64,722,000
Impairment losses on receivables related to contracts with customers	$ 0	0
Percentage of likelihood for term more likely than not as it relates to income taxes	50.00%
Transfer of debt securities from held-to-maturity to available-for-sale	$ 270,331,000	$ 0	$ 0
Accounting Standards Update 2017-12
Transfer of debt securities from held-to-maturity to available-for-sale	$ 270,331,000
Accounting Standards Update 2014-09
Number of Steps to Achieve Core Revenue Recognition Principal | step	5
Accounting Standards Update 2017-08
Effect of cumulative change on retained earnings from applying new accounting pronouncement	$ 24,102,000
Accounting Standards Update 2016-02
Effect of cumulative change on assets from applying new accounting pronouncement	36,042,000
Effect of cumulative change on liabilities from applying new accounting pronouncement	$ 37,384,000
Consumer and Other
Minimum Number of Days Delinquent to Charge Off Loans	120 days
Minimum Range
Number of years for home equity loan origination term	10 years
Minimum Range | Office Buildings
Useful life of premises and equipment	15 years
Minimum Range | Furniture, fixtures and equipment
Useful life of premises and equipment	3 years
Maximum Range
Number of years for home equity loan origination term	15 years
Maximum Range | Office Buildings
Useful life of premises and equipment	40 years
Maximum Range | Furniture, fixtures and equipment
Useful life of premises and equipment	10 years