Income Taxes - Deferred Taxes and Liabilities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation Allowance [Line Items]
Deferred Tax Assets, Derivative Instruments	$ 6,800,000	$ 15,917,000
Deferred Tax Asset - basis in securities	5,661,000	9,307,000
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Provision for Loan Losses	1,862,000	2,602,000
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost	532,000	1,648,000
Deferred Tax Assets, Capital Loss Carryforwards	36,000	56,000
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Compensation	778,000	1,222,000
Tax Credit Carryforward, Amount	200,000
Deferred Tax Assets, Other	74,000	2,000
Deferred Tax Assets, Gross	15,707,000	30,698,000
Deferred Tax Liabilities, Other Comprehensive Income	12,376,000	16,889,000
Deferred Tax Liabilities, Other	1,283,000	1,518,000
Deferred Tax Liabilities, Gross	13,659,000	18,407,000
Deferred tax asset, net	2,048,000	12,291,000
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	1,365,000	0	$ 0
Capital Loss Carryforward [Member]
Valuation Allowance [Line Items]
Deferred Tax Assets, Valuation Allowance	(36,000)	(56,000)
Expired Capital Loss Carryforward [Member]
Valuation Allowance [Line Items]
Deferred Tax Assets, Capital Loss Carryforwards		2,100,000
Tax Credit Carryforward, Amount	$ 0	$ 5,900,000