Derivative Financial Instruments (Rollforward of Amounts in Accumulated Other Comprehensive Income Related to Interest Rate Swaps Designated as Cash Flow Hedges) (Details) - Interest Rate Contract - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Rollforward of AOCI from Cash Flow Hedging Derivatives [Roll Forward]
Unrealized gain (loss) at beginning of period	$ 6,944	$ (3,529)
Amount reclassified from accumulated other comprehensive income to interest expense on deposits and junior subordinated debentures	(19)	3,120
Amount of gain recognized in other comprehensive income	4,977	7,353
Unrealized gain at end of period	$ 11,902	$ 6,944