Investment Securities (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Schedule of Available-for-sale Securities [Line Items]
AFS securities pledged as collateral	$ 427,800,000		$ 427,800,000
Proceeds from sales of securities available-for-sale			500,101,000	$ 185,533,000
Gross realized gains on sale of securities	958,000	$ 1,300,000	8,100,000	3,300,000
Gross realized losses on sale of securities	(132,000)	(119,000)	(707,000)	(498,000)
Available-for-sale Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales of securities available-for-sale	$ 130,500,000	$ 98,300,000	492,700,000	$ 182,700,000
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification			$ 7,100,000