Derivative Instruments and Balance Sheet Offsetting (Net Gains (Losses) Recorded in Other Comprehensive Income and the Income Statement) (Details) - Designated as hedging - Interest rate swaps $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Derivative [Line Items]
Amount of gain (loss) recognized in other comprehensive income (Effective portion)	$ 4,263
Amount of gain (loss) reclassified from other comprehensive income to interest income or expense (Effective portion)	(1,633)
Amount of gain (loss) recognized in other noninterest income (Ineffective portion)	$ (3)