Accumulated Other Comprehensive Loss, Net of Tax (Schedule of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ (78,106)	$ (56,261)	$ (48,549)
Other comprehensive income (loss) before reclassifications	(8,308)	(31,148)	(12,024)
Amounts reclassified from accumulated other comprehensive (loss) income	9,421	9,303	4,312
Other comprehensive income (loss), net of tax	1,113	(21,845)	(7,712)
Ending Balance	(76,993)	(78,106)	(56,261)
Available For Sale and Transferred Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(6,407)	16,421	(2,617)
Other comprehensive income (loss) before reclassifications	(8,901)	(22,512)	21,811
Amounts reclassified from accumulated other comprehensive (loss) income	(168)	(316)	(2,773)
Other comprehensive income (loss), net of tax	(9,069)	(22,828)	19,038
Ending Balance	(15,476)	(6,407)	16,421
Derivative Instruments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(22,980)	(25,530)	(18,206)
Other comprehensive income (loss) before reclassifications	825	(3,136)	(12,506)
Amounts reclassified from accumulated other comprehensive (loss) income	5,087	5,686	5,182
Other comprehensive income (loss), net of tax	5,912	2,550	(7,324)
Ending Balance	(17,068)	(22,980)	(25,530)
Defined Benefit Pension and Postretirement Benefit Plans [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(48,719)	(47,152)	(27,726)
Other comprehensive income (loss) before reclassifications	(232)	(5,500)	(21,329)
Amounts reclassified from accumulated other comprehensive (loss) income	4,502	3,933	1,903
Other comprehensive income (loss), net of tax	4,270	(1,567)	(19,426)
Ending Balance	$ (44,449)	$ (48,719)	$ (47,152)