(Schedule of Net Funded Status) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Change in plan assets, at fair value:
Fair value of plan assets, ending balance	$ 236,781
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation, end of year		$ 339,661	$ 354,402
Change in projected benefit obligation:
Projected Benefit Obligation, Beginning Balance	355,642	308,834
Service cost	830	728	2,339
Interest cost	14,069	14,337	12,814
Plan amendments	0	0
Participant contributions	0	0
Actuarial gains/losses and changes in assumptions	(10,469)	50,115
Benefits paid	(19,252)	(18,372)
Projected Benefit Obligation, Ending Balance	340,820	355,642	308,834
Change in plan assets, at fair value:
Fair value of plan assets, beginning balance	257,355	257,510
Actual return on plan assets	(2,849)	16,663
Participant contributions	0	0
Employer contributions	1,527	1,554
Benefits paid	(19,252)	(18,372)
Fair value of plan assets, ending balance	236,781	257,355	257,510
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded Status	(104,039)	(98,287)
Amounts recognized in AOCI before income taxes:
Prior service cost (credit)	308	2,587
Net actuarial loss	103,477	99,715
Amount recognized in AOCI	103,785	102,302
Postretirement Benefits
Change in projected benefit obligation:
Projected Benefit Obligation, Beginning Balance	15,164	15,544
Service cost	165	65	99
Interest cost	575	655	563
Plan amendments	(7,657)	(1,979)
Participant contributions	1,805	1,851
Actuarial gains/losses and changes in assumptions	(446)	2,046
Benefits paid	(2,765)	(3,018)
Projected Benefit Obligation, Ending Balance	6,841	15,164	15,544
Change in plan assets, at fair value:
Fair value of plan assets, beginning balance	0	0
Actual return on plan assets	0	0
Participant contributions	1,805	1,851
Employer contributions	960	1,167
Benefits paid	(2,765)	(3,018)
Fair value of plan assets, ending balance	0	0	$ 0
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded Status	(6,841)	(15,164)
Amounts recognized in AOCI before income taxes:
Prior service cost (credit)	(12,389)	(5,370)
Net actuarial loss	4,364	5,138
Amount recognized in AOCI	$ (8,025)	$ (232)