Retirement Plans and Postretirement Medical Benefits (Benefit Obligations and Funded Status) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits | United States
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 1,729,515	$ 1,612,551
Projected benefit obligation
Benefit obligation - beginning of year	1,613,054	1,501,140
Service cost	86	83	$ 92
Interest cost	52,103	63,171	61,490
Actuarial loss (gain)	185,306	160,390
Foreign currency changes	0	0
Settlements and curtailments	(3,854)	(6,684)
Benefits paid	(116,736)	(105,046)
Benefit obligation - end of year	1,729,959	1,613,054	1,501,140
Fair value of plan assets
Fair value of plan assets - beginning of year	1,487,018	1,327,034
Actual return on plan assets	225,812	261,579
Company contributions	9,546	10,135
Settlements and curtailments	(3,854)	(6,684)
Foreign currency changes	0	0
Benefits paid	(116,736)	(105,046)
Fair value of plan assets - end of year	1,601,786	1,487,018	1,327,034
Amounts recognized in the Consolidated Balance Sheets
Noncurrent asset	465	383
Current liability	(5,843)	(9,019)
Noncurrent liability	(122,795)	(117,401)
Funded status	(128,173)	(126,037)
Pension Benefits | Foreign
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	829,413	745,658
Projected benefit obligation
Benefit obligation - beginning of year	746,942	662,644
Service cost	1,650	1,543	2,159
Interest cost	13,379	17,853	18,089
Actuarial loss (gain)	76,006	68,385
Foreign currency changes	29,128	25,452
Settlements and curtailments	(15,171)	(2,682)
Benefits paid	(21,260)	(26,253)
Benefit obligation - end of year	830,674	746,942	662,644
Fair value of plan assets
Fair value of plan assets - beginning of year	668,308	562,517
Actual return on plan assets	78,120	98,006
Company contributions	9,674	10,085
Settlements and curtailments	(15,171)	(1,773)
Foreign currency changes	22,968	25,726
Benefits paid	(21,260)	(26,253)
Fair value of plan assets - end of year	742,639	668,308	562,517
Amounts recognized in the Consolidated Balance Sheets
Noncurrent asset	26,053	20,020
Current liability	(1,444)	(1,313)
Noncurrent liability	(112,644)	(97,341)
Funded status	(88,035)	(78,634)
Nonpension postretirement benefit plans
Projected benefit obligation
Benefit obligation - beginning of year	164,104	166,476
Service cost	885	967	1,405
Interest cost	4,993	6,584	6,640
Actuarial loss (gain)	11,496	6,930
Foreign currency changes	340	674
Benefits paid	(12,608)	(17,527)
Benefit obligation - end of year	169,210	164,104	166,476
Fair value of plan assets
Fair value of plan assets - beginning of year	0	0
Company contributions	12,608	17,527
Benefits paid	(12,608)	(17,527)
Fair value of plan assets - end of year	0	0	$ 0
Amounts recognized in the Consolidated Balance Sheets
Current liability	(15,372)	(16,132)
Noncurrent liability	(153,838)	(147,972)
Funded status	(169,210)	(164,104)
Nonpension postretirement benefit plans | United States
Projected benefit obligation
Benefit obligation - beginning of year	150,000
Benefit obligation - end of year	$ 153,000	$ 150,000