Fair Value (Details Textual) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) Security	Dec. 31, 2016 Security
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Number of debt securities with other-than-temporary impairment | Security	1	1
Maturity period of short-term borrowings	one year or less
Period of swap rate	25 years
Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value input discount rate	9.10%
Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value input discount rate	14.74%
PreTSL XXIII
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value input discount rate	14.74%
Securities maturity date	2036-12
Securities Nonperforming Collateral Amount	$ 209.0
Securities Performing Collateral Amount	861.0
Estimated cash flows	42.6
Current principal value	$ 26.1
Trapeza IX
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value input discount rate	9.10%
Securities maturity date	2038-01
Securities Nonperforming Collateral Amount	$ 6.8
Securities Performing Collateral Amount	200.0
Estimated cash flows	41.6
Current principal value	$ 23.8
Trust preferred securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Number of debt securities with other-than-temporary impairment | Security	1	1
Period frequency of projected prepayment rate	1 year
Projected Prepayments, minimum fixed rate coupons	8.00%
Projected Prepayments, percentage of fair value input for banks	1.00%
Projected prepayment, percentage of fair value for collateral by REITs	0.00%
Projected prepayment, percentage of fair value for collateral for insurance companies	2.00%
Annually projected defaults percentage for healthy banks	2.00%
Period frequency of projected default rate	2 years
Projected defaults rate for healthy banks	0.36%
Projected Recoveries, percentage for insurance companies, REITs and insolvent banks	0.00%
Projected recovery, percentage for projected bank deferrals	10.00%
Projected Bank Deferrals lagged	2 years
Trust preferred securities | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value input discount rate	9.10%	9.69%
Trust preferred securities | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value input discount rate	14.74%	15.11%