Securities (Narrative) (Details)	3 Months Ended
	Mar. 31, 2019 USD ($) Investment	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Debt and Equity Securities, FV-NI [Line Items]
Held to maturity securities, transferred from available for sale	$ 0
Investment Security Losses, net	(200,000)	$ (200,000)
Gross proceeds from sale of securities	$ 127,500,000	2,000,000
Number of securities in an unrealized loss position | Investment	1,234
Total fair value	$ 28,900,000,000
Total unrealized losses	268,900,000
Debt securities, unrealized losses	268,900,000		$ 357,100,000
OTTI losses	0	$ 200,000
CRA Eligible, Mortgage Backed Securities
Debt and Equity Securities, FV-NI [Line Items]
OTTI losses	0
Government Sponsored Agency
Debt and Equity Securities, FV-NI [Line Items]
Total unrealized losses	124,600,000
Debt securities, unrealized losses	124,600,000		150,500,000
Corporate Debt
Debt and Equity Securities, FV-NI [Line Items]
Total unrealized losses	14,400,000
Debt securities, unrealized losses	$ 14,400,000		22,900,000
Percent of corporate debt portfolio	36.00%
Other
Debt and Equity Securities, FV-NI [Line Items]
Total unrealized losses	$ 64,600,000
Debt securities, unrealized losses	$ 64,600,000		$ 69,600,000