Fair Value of Assets and Liabilities (Details Textual) - Security	6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Number of debt securities with other-than-temporary impairment		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%
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			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%
Trust preferred securities | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value input discount rate			14.74%