Other Comprehensive Income (Loss) (Changes in Accumulated Other Comprehensive Income (Loss) by Component (Net of Income Taxes)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Changes in Accumulated Other Comprehensive Income (Loss) by Component [Roll Forward]
Beginning balance	$ (55,659)
Other comprehensive income, Net of Tax Amount	908	$ 29,079
Ending balance	(54,751)
Total [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component [Roll Forward]
Beginning balance	(55,659)	(29,819)
Other comprehensive income (loss) before reclassifications	5,596	29,010
Amounts reclassified from accumulated other comprehensive income (loss)	(4,688)	69
Other comprehensive income, Net of Tax Amount	908	29,079
Ending balance	(54,751)	(740)
Net Unrealized Gains (Losses) on Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component [Roll Forward]
Beginning balance	(12,217)	(12,504)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	40	168
Other comprehensive income, Net of Tax Amount	40	168
Ending balance	(12,177)	(12,336)
Net Unrealized Gains (Losses) on Investment Securities Available for Sale [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component [Roll Forward]
Beginning balance	(44,324)	(18,222)
Other comprehensive income (loss) before reclassifications	5,596	29,010
Amounts reclassified from accumulated other comprehensive income (loss)	(4,716)	(41)
Other comprehensive income, Net of Tax Amount	880	28,969
Ending balance	(43,444)	10,747
Post-Retirement Unfunded Health Benefit [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component [Roll Forward]
Beginning balance	882	907
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	(12)	(58)
Other comprehensive income, Net of Tax Amount	(12)	(58)
Ending balance	$ 870	$ 849