Employee Benefits (Other Comprehensive Income, Other Postretirement Benefit Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (gain) loss	$ 5,898	$ (12,634)		$ 20,053
Prior service benefit	0	0		(32,697)
Amortization of:
Prior service benefit	9,657	9,657		7,407
Net gain	(6,387)	(6,776)		(4,965)
Other Postretirement Benefit Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (gain) loss	(3,863)	(10,586)		10,143
Prior service benefit	0	0	[1]	(32,697)	[1]
Amortization of:
Prior service benefit	6,151	6,151		3,901
Net gain	2,166	1,678		2,374
Total recognized in other comprehensive income	$ 4,454	$ (2,757)		$ (16,279)

[1] (a) During October 2016, the Company approved and communicated a plan amendment that resulted in a remeasurement of the Company's OPEB Plan. Effective January 1, 2017, retirees and dependents that are less than 65 years of age are offered a choice between a $1,000 and $2,250 deductible plan. Additionally, retirees and dependents that are 65 years of age or greater were covered by a fully insured Medicare advantage plan.