Investment Securities (Pooled Trust Preferred Collateralized Debt Obligations) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($) entity	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Fair Value, available for sale	$ 360,747		$ 277,378
Unrealized loss	(10,534)		$ (3,532)
Realized losses YTD	$ 666	$ 453
Percentage of recovery estimate depository institutions	10.00%
Percentage of recovery estimate insurance companies	15.00%
Pooled Trust Preferred Security [Member]
Original Par	$ 3,000
Pooled Trust Preferred Security [Member] | U.S. Capital Funding I [Member]
Class	B1
Original Par	$ 3,000
Book Value	2,997
Fair Value, available for sale	2,120
Unrealized loss	(877)
Realized losses YTD
Number of Banks / Insurance Cos. Currently Performing | entity	26
Total Number of Banks and Insurance Cos. In Issuance (Unique) | entity	30
Actual Deferrals/Defaults (as a % of original collateral)	7.95%
Total Projected Defaults (as a % of performing collateral)	5.92%
Excess subordination (after taking into account best estimate of future deferrals/defaults)	12.29%
Minimum | Pooled Trust Preferred Security [Member] | U.S. Capital Funding I [Member]
Class	Caa1