Pension and Postretirement Plans (Total Benefit/Cost) (Details 1) - USD ($) $ in Thousands	3 Months Ended							9 Months Ended		12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Cost (Benefit)								$ (45,081)	$ (51,637)
Early retirement programs and special separation benefit expense								3,734	8,374
Total Cost (Benefit)	$ (16,255)	$ (12,415)	$ (12,407)	$ (18,686)	$ (14,237)	$ (18,807)	$ (13,052)	(41,077)	(46,095)	$ (64,780)	$ (20,727)
Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	6,090				6,976			20,593	21,489
Interest cost	13,516				12,894			39,077	38,870
Expected return on assets	(33,673)				(29,877)			(96,771)	(90,644)
Amortization of prior service cost (credit)	79				83			241	247
Recognized actuarial loss (gain)	(6,057)				(7,280)			(6,057)	(21,599)
Net Periodic Cost (Benefit)	(20,045)				(17,204)			(42,917)	(51,637)
Curtailment gain	(3,267)				0			(3,267)	0
Early retirement programs and special separation benefit expense	3,734				3,884			3,734	8,374
Total Cost (Benefit)	(19,578)				(13,320)			(42,450)	(43,263)
Supplemental Executive Retirement Plan (SERP) [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	464				373			1,482	1,119
Interest cost	1,140				1,086			3,410	3,257
Amortization of prior service cost (credit)	115				12			343	35
Recognized actuarial loss (gain)	630				374			2,385	1,124
Net Periodic Cost (Benefit)	2,349				1,845			7,620	5,535
Early retirement programs and special separation benefit expense	0				2,422			0	2,422
Total Cost (Benefit)	2,349				4,267			7,620	7,957
Other Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	333				375			999	1,125
Interest cost	325				362			974	1,086
Amortization of prior service cost (credit)	(126)				(196)			(377)	(587)
Recognized actuarial loss (gain)	(249)				(519)			(747)	(1,557)
Net Periodic Cost (Benefit)	$ 283				$ 22			$ 849	$ 67