Pension and Postretirement Plans (Total Benefit/Cost) (Details 1) - USD ($) $ in Thousands	3 Months Ended							9 Months Ended		12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Cost (Benefit)	$ 5,142	$ 4,963	$ 5,221	$ 4,491	$ 4,473	$ 4,317	$ 4,940	$ 15,326	$ 13,730	$ 18,221	$ 18,687
Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	5,142				4,473			15,326	13,730
Interest cost	11,743				11,844			35,078	34,943
Expected return on assets	(30,832)				(31,969)			(91,955)	(97,251)
Amortization of prior service cost (credit)	824				36			2,058	114
Recognized actuarial loss (gain)	0				(2,974)			0	(6,994)
Net Periodic Cost (Benefit)	(13,123)				(18,590)			(39,493)	(55,458)
Curtailment gain	0				0			0	(806)
Special separation benefit expense	(175)				0			6,432	0
Net Periodic Cost (Benefit)	(13,298)				(18,590)			(33,061)	(56,264)
Supplemental Executive Retirement Plan (SERP) [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	214				205			643	614
Interest cost	1,079				967			3,236	2,899
Amortization of prior service cost (credit)	85				77			254	233
Recognized actuarial loss (gain)	579				600			1,736	1,802
Net Periodic Cost (Benefit)	1,957				1,849			5,869	5,548
Other Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0				267			0	803
Interest cost	72				170			216	509
Amortization of prior service cost (credit)	(1,841)				(44)			(5,522)	(132)
Recognized actuarial loss (gain)	(1,090)				(921)			(3,270)	(2,764)
Net Periodic Cost (Benefit)	$ (2,859)				$ (528)			$ (8,576)	$ (1,584)