Investment Securities Other investment disclosures (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018		Jan. 01, 2017	[2]
Schedule of Investments [Line Items]
Weighted average remaining maturity available for sale	7 years 7 months 30 days	8 years 1 month 20 days
Available for sale securities callable before maturity	$ 217,000,000	$ 184,900,000
Weighted average remaining maturity held to maturity	11 years	11 years 10 months 31 days
Qualified affordable housing project investments	$ 54,400,000	$ 39,400,000
Affordable housing project investments, commitment	23,000,000	11,500,000
Affordable housing project impairment	0	0
Income Tax Expense
Schedule of Investments [Line Items]
Affordable housing project investments, amortization	3,000,000	2,700,000	$ 1,600,000
Affordable housing tax credits and other tax benefits	$ 2,900,000	$ 2,200,000	$ 1,700,000
Accumulated Other Comprehensive Income/ (Loss)
Schedule of Investments [Line Items]
Reclassification due to change in accounting principle				$ (334,000)	[1]	$ (1,535,000)
Retained Earnings
Schedule of Investments [Line Items]
Reclassification due to change in accounting principle				334,000	[1]	$ 1,535,000
Accounting Standards Update 2016-01 | Accumulated Other Comprehensive Income/ (Loss)
Schedule of Investments [Line Items]
Reclassification due to change in accounting principle				(339,000)
Accounting Standards Update 2016-01 | Retained Earnings
Schedule of Investments [Line Items]
Reclassification due to change in accounting principle				$ 339,000

[1] Reclassification due to the adoption of ASU 2016-01 and ASU 2017-12. See Part II. Item 8. “Financial Statements and Supplementary Data - Note 1: Basis of Presentation and Summary of Significant Accounting Policies.”

[2] Reclassification due to the adoption of ASU 2018-02. See Part II. Item 8. “Financial Statements and Supplementary Data - Note 1: Basis of Presentation and Summary of Significant Accounting Policies.”