Derivative Instruments (Narrative) (Details) - USD ($)	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 26, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative, fair value	$ 5,900,000			$ 4,300,000
Valuation adjustment	2,300,000
Loss on sale of outstanding commitments	(119,000)	$ (1,700,000)
Collateral requirements	30,600,000			43,800,000
Variation margin, amount reducing derivative asset	8,900,000			1,500,000
Visa derivative
Derivative [Line Items]
Escrow Deposit			$ 600,000,000
Fixed Rate Residential Mortgage
Derivative [Line Items]
Commitments to fund fixed-rate mortgage loans	69,700,000			49,300,000
Unrealized gain (loss) on fair value of fixed-rate mortgage loans to customers	(366,000)	$ (416,000)
Sale of outstanding commitments	86,000,000			72,500,000
Interest Rate Swap
Derivative [Line Items]
Notional amount of interest rate swap contracts	1,670,000,000
Increase in derivative, notional amount	$ 201,400,000
Cash Flow Hedges
Derivative [Line Items]
Derivative instruments				0
Fair Value Hedges
Derivative [Line Items]
Derivative instruments				$ 0