Fair Value of Assets and Liabilities (FV on recurring or nonrecurring basis-level 3 inputs) (Details 3) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Interest Rate Lock Commitments | Pricing Model
Level 3 Assets and Liabilities, Fair Value and Fair Value Unobservable Inputs
Weighted Average Closing Ratio (as a percent)	92.81%	93.25%
Interest Rate Derivative Instruments Not Designated as Hedging Instruments at Fair Value, Net	$ 937	$ 789
Interest Rate Swap Agreements | Discounted Cash Flow
Level 3 Assets and Liabilities, Fair Value and Fair Value Unobservable Inputs
Weighted Average Credit Factor (as a percent)	0.02%	0.10%
Interest Rate Derivative Instruments Not Designated as Hedging Instruments at Fair Value, Net	$ (390)	$ 105
Mortgage Servicing Rights | Discounted Cash Flow
Level 3 Assets and Liabilities, Fair Value and Fair Value Unobservable Inputs
Weighted Average Constant Prepayment Rate (as a percent)	7.07%	8.50%
Weighted Average Discount Rate (as a percent)	9.77%	8.87%
Mortgage Servicing Rights, at Fair Value	$ 30,004	$ 28,170