Retirement Benefits (Postretirement Health Care and Life Insurance Benefit Plans) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net periodic benefit cost:
Mark-to-market actuarial net loss (gain)	$ 13,300	$ (16,500)
Change in benefit obligation:
Mark-to-market actuarial net loss (gain)	13,300	(16,500)
Actuarial loss (gain)				$ 17,900
Amounts recognized in the balance sheet:
Accrued expenses and other current liabilities	(73,759)	(52,867)	$ (73,759)	(52,867)
Postretirement and pension liabilities	(174,021)	(166,681)	(174,021)	(166,681)
Postretirement Health Care And Life Insurance Benefit Plans [Member]
Net periodic benefit cost:
Interest cost			702	732
Service cost			2
Change in benefit obligation:
Benefit obligation at beginning of year			17,198	20,725
Service cost			2
Interest cost			702	732
Benefits paid			(1,833)	(1,679)
Actuarial loss (gain)			1,080	(2,580)
Benefit obligation at end of year	17,149	17,198	17,149	17,198	$ 20,725
Fair value of plan assets at beginning of year
Employer contributions			1,836	1,679
Benefits paid			(1,836)	(1,679)
Fair value of plan assets at end of year
Amounts recognized in the balance sheet:
Accrued expenses and other current liabilities	(1,945)	(1,966)	(1,945)	(1,966)
Postretirement and pension liabilities	(15,204)	(15,232)	(15,204)	(15,232)
Funded status	$ 17,149	$ 17,198	$ 17,149	$ 17,198
Weighted-average assumptions as of December 31:
Discount rate	3.25%	4.30%	3.25%	4.30%
Current trend rate for health care costs	6.10%	6.30%	6.10%	6.30%
Ultimate trend rate for health care costs	4.50%	4.50%	4.50%	4.50%
Year that ultimate trend rate is reached			2036	2036
Postretirement Health Care And Life Insurance Benefit Plans [Member] | United States [Member]
Net periodic benefit cost:
Interest cost			$ 702	$ 732	843
Service cost			2
Mark-to-market actuarial net loss (gain)			1,080	(2,580)	458
Total net periodic benefit cost (credit)			1,784	(1,848)	1,301
One-percentage-point change in the assumed health care cost trend rates
Effect on total of service and interest cost components, Percentage Point Increase			38
Effect on total of service and interest cost components, Percentage Point Decrease			(34)
Effect on postretirement benefit obligation, Percentage Point Increase			877
Effect on postretirement benefit obligation, Percentage Point Decrease			(773)
Change in benefit obligation:
Service cost			2
Interest cost			702	732	843
Mark-to-market actuarial net loss (gain)			1,080	(2,580)	458
Total net periodic benefit (income) cost			$ 1,784	$ (1,848)	$ 1,301
Weighted-average assumptions as of December 31:
Discount rate			4.30%	3.70%	4.20%
Current trend rate for health care costs			6.30%	6.40%	6.50%
Ultimate trend rate for health care costs			4.50%	4.50%	4.50%
Year that ultimate trend rate is reached			2036	2036	2036