Other Comprehensive Income (Loss) (Changes in Accumulated Other Comprehensive Income (Loss) by Component (Net of Income Taxes)) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Changes in Accumulated Other Comprehensive Income (Loss) by Component [Roll Forward]
Beginning balance			$ (55,659)
Other comprehensive income, Net of Tax Amount	$ 6,886	$ 11,745	7,794	$ 40,824
Ending balance	(47,865)		(47,865)
Total
Changes in Accumulated Other Comprehensive Income (Loss) by Component [Roll Forward]
Beginning balance	(54,751)	(740)	(55,659)	(29,819)
Other comprehensive income (loss) before reclassifications	6,857	11,712	12,453	40,722
Amounts reclassified from accumulated other comprehensive income (loss)	29	33	(4,659)	102
Other comprehensive income, Net of Tax Amount	6,886	11,745	7,794	40,824
Ending balance	(47,865)	11,005	(47,865)	11,005
Net unrealized gains (losses) on cash flow hedges
Changes in Accumulated Other Comprehensive Income (Loss) by Component [Roll Forward]
Beginning balance	(12,177)	(12,336)	(12,217)	(12,504)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	40	39	80	207
Other comprehensive income, Net of Tax Amount	40	39	80	207
Ending balance	(12,137)	(12,297)	(12,137)	(12,297)
Net unrealized gains (losses) on investment securities available for sale
Changes in Accumulated Other Comprehensive Income (Loss) by Component [Roll Forward]
Beginning balance	(43,444)	10,747	(44,324)	(18,222)
Other comprehensive income (loss) before reclassifications	6,857	11,712	12,453	40,722
Amounts reclassified from accumulated other comprehensive income (loss)	1	0	(4,715)	(41)
Other comprehensive income, Net of Tax Amount	6,858	11,712	7,738	40,681
Ending balance	(36,586)	22,459	(36,586)	22,459
Post-retirement unfunded health benefit
Changes in Accumulated Other Comprehensive Income (Loss) by Component [Roll Forward]
Beginning balance	870	849	882	907
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	(12)	(6)	(24)	(64)
Other comprehensive income, Net of Tax Amount	(12)	(6)	(24)	(64)
Ending balance	$ 858	$ 843	$ 858	$ 843