Securities - Narrative (Details)		9 Months Ended		12 Months Ended
	Jan. 01, 2019 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Investment [Line Items]
Transferred Securities, Unrealized Loss, Before Tax		$ 3,800,000		$ 15,300,000
Securities transferred, Unrealized Loss, Net of Tax		3,000,000.0		12,100,000
Fair value of securities transferred from AFS to HTM		$ 0		0
AFS securities and HTM securities with other-than-temporary impairment		0
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Net realized gain (loss) on AFS securities		$ 714,000	$ (1,900,000)
Gross realized gains on AFS securities		5,600,000	1,900,000
Gross realized losses on AFS securities		4,900,000	3,800,000
Carrying value of investment securities pledged as collateral		871,900,000		1,080,000,000.00
Equity investments		$ 12,388,000		$ 12,093,000
Equity investments with other-than-temporary impairment		0
Federal Home Loan Bank stock with other-than-temporary impairment		0
Debt Securities, Held-to-maturity, Sale or Transfer of Investment [Abstract]
Sale of HTM portfolio		$ 0	$ 0
Accounting Standards Update 2017-08
Investment [Line Items]
Cumulative effect on Retained Earnings, before tax	$ (16,500,000)