Business and Summary of Significant Accounting Policies (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2017 USD ($) reporting_unit_level	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Feb. 28, 2018 USD ($)
Accounting Policy [Line Items]
Trading Securities		$ 0	$ 0
Equity Method Investment, Ownership Percentage		100.00%
Loans Held-for-sale		$ 8,103,000	14,836,000
Financing Receivable, Individually Evaluated for Impairment		$ 13,590,000	20,254,000	$ 15,235,000
Number of Reporting Unit Levels | reporting_unit_level		2
Goodwill impairment			0	0
BOLI single carrier percentage of Tier I capital		15.00%
BOLI CSV percentage of Tier I Capital		25.00%
HTM securities		$ 94,073,000	94,609,000
AFS securities		$ 789,899,000	779,867,000
Stockholders' Equity Note, Stock Split, Conversion Ratio	1.5	1.5
Minimum [Member]
Accounting Policy [Line Items]
Financing Receivable, Individually Evaluated for Impairment		$ 500,000	250,000
Finite-lived intangible asset, useful life (years)		5 years
Maximum [Member]
Accounting Policy [Line Items]
Finite-lived intangible asset, useful life (years)		10 years
Residential real estate
Accounting Policy [Line Items]
Term to maturity (years)		30 years
Financing Receivable, Individually Evaluated for Impairment		$ 5,171,000	$ 4,348,000	$ 6,026,000
Accumulated Other Comprehensive Income (Loss) | Subsequent Event [Member] | Accounting Standards Update 2018-02 [Member]
Accounting Policy [Line Items]
Reclassification adjustment					$ (3,500,000)
Retained Earnings [Member] | Subsequent Event [Member] | Accounting Standards Update 2018-02 [Member]
Accounting Policy [Line Items]
Reclassification adjustment					$ 3,500,000