Other Comprehensive (Loss) Income (Components of OCI) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive (loss) income, before tax	$ (12,289)	$ 1,432
Total other comprehensive income (loss), tax effect	3,242	(574)
Reclassification adjustment for losses (gains) included in net income, after tax	(74)	(37)
Total other comprehensive (loss) income	(9,047)	858
Unrealized gains and losses on securities available for sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net (losses) gains arising during the period, before tax	(13,093)	1,287
Reclassification adjustment for losses (gains) included in net income, before tax	0	0
Total other comprehensive (loss) income, before tax	(13,093)	1,287
Net (losses) gains arising during the period, tax effect	3,454	(516)
Reclassification adjustment for losses (gains) included in net income, tax effect	0	0
Total other comprehensive income (loss), tax effect	3,454	(516)
Net (losses) gains arising during the period, after tax	(9,639)	771
Reclassification adjustment for losses (gains) included in net income, after tax	0	0
Total other comprehensive (loss) income	(9,639)	771
Unrealized gains (losses) on derivatives (cash flow hedges) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive (loss) income, before tax	720	92
Total other comprehensive income (loss), tax effect	(190)	(37)
Total other comprehensive (loss) income	530	55
Post-retirement obligations [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive (loss) income, before tax	84	53
Total other comprehensive income (loss), tax effect	(22)	(21)
Total other comprehensive (loss) income	$ 62	$ 32