Derivative Instruments and Balance Sheet Offsetting (Notional Amount and Fair Value) (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Derivative instruments
Notional Amount	$ 853,594,000	$ 90,911,000
Gross Derivative Assets	8,215,000	2,018,000
Gross Derivative Liabilities	6,359,000	1,979,000
Credit valuation adjustments for counterparty credit risk	99,000	0
Not designated as hedging | Customer-initiated derivatives
Derivative instruments
Notional Amount	600,598,000	0
Gross Derivative Assets	4,406,000	0
Gross Derivative Liabilities	4,141,000	0
Not designated as hedging | Forward contracts related to mortgage loans to be delivered for sale
Derivative instruments
Notional Amount	140,155,000	33,787,000
Gross Derivative Assets	635,000	144,000
Gross Derivative Liabilities	0	57,000
Not designated as hedging | Interest rate lock commitments
Derivative instruments
Notional Amount	76,034,000	23,421,000
Gross Derivative Assets	956,000	42,000
Gross Derivative Liabilities	0	90,000
Not designated as hedging | Power Equity CD
Derivative instruments
Notional Amount	36,807,000	33,703,000
Gross Derivative Assets	2,218,000	1,832,000
Gross Derivative Liabilities	$ 2,218,000	$ 1,832,000