Retirement Plans and Postretirement Medical Benefits (Benefit Obligations and Funded Status) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
United States
Fair value of plan assets
Fair value of plan assets - beginning of year	$ 1,557,907
Fair value of plan assets - end of year	1,327,034	$ 1,557,907
Foreign
Fair value of plan assets
Fair value of plan assets - beginning of year	632,710
Fair value of plan assets - end of year	562,517	632,710
Pension Benefits \| United States
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	1,500,691	1,726,824
Projected benefit obligation
Benefit obligation - beginning of year	1,727,737	1,678,097
Service cost	92	132	$ 105
Interest cost	61,490	68,611	73,699
Plan participants' contributions	0	0
Actuarial (gain) loss	(124,298)	92,789
Foreign currency changes	0	0
Plan amendments	0	0
Settlement / curtailment	(82,273)	0
Benefits paid	(81,608)	(111,892)
Benefit obligation - end of year	1,501,140	1,727,737	1,678,097
Fair value of plan assets
Fair value of plan assets - beginning of year	1,557,907	1,464,082
Actual return on plan assets	(73,745)	199,749
Company contributions	6,753	5,968
Plan participants' contributions	0	0
Settlement / curtailment	(82,273)	0
Foreign currency changes	0	0
Benefits paid	(81,608)	(111,892)
Fair value of plan assets - end of year	1,327,034	1,557,907	1,464,082
Amounts recognized in the Consolidated Balance Sheets
Noncurrent asset	277	392
Current liability	(10,975)	(8,362)
Noncurrent liability	(163,408)	(161,860)
Funded status	(174,106)	(169,830)
Pension Benefits \| Foreign
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	659,628	737,580
Projected benefit obligation
Benefit obligation - beginning of year	751,373	688,172
Service cost	2,159	2,274	2,148
Interest cost	18,089	18,836	21,886
Plan participants' contributions	7	6
Actuarial (gain) loss	(41,995)	2,098
Foreign currency changes	(40,559)	64,236
Plan amendments	9,009	0
Settlement / curtailment	(6,703)	0
Benefits paid	(28,736)	(24,249)
Benefit obligation - end of year	662,644	751,373	688,172
Fair value of plan assets
Fair value of plan assets - beginning of year	632,710	547,290
Actual return on plan assets	(17,043)	46,542
Company contributions	10,939	13,081
Plan participants' contributions	7	6
Settlement / curtailment	0	0
Foreign currency changes	(35,360)	50,040
Benefits paid	(28,736)	(24,249)
Fair value of plan assets - end of year	562,517	632,710	547,290
Amounts recognized in the Consolidated Balance Sheets
Noncurrent asset	14,225	19,139
Current liability	(1,197)	(1,188)
Noncurrent liability	(113,155)	(136,614)
Funded status	(100,127)	(118,663)
Nonpension postretirement benefit plans
Projected benefit obligation
Benefit obligation - beginning of year	188,841	189,772
Service cost	1,405	1,727	2,046
Interest cost	6,640	7,100	7,969
Plan participants' contributions	3,200	3,820
Actuarial (gain) loss	(11,304)	5,134
Foreign currency changes	(1,178)	1,066
Settlement / curtailment	(533)	0
Benefits paid	(20,596)	(19,778)
Benefit obligation - end of year	166,475	188,841	189,772
Fair value of plan assets
Fair value of plan assets - beginning of year	0	0
Company contributions	17,396	15,958
Plan participants' contributions	3,200	3,820
Benefits paid	(20,596)	(19,778)
Fair value of plan assets - end of year	0	0	$ 0
Amounts recognized in the Consolidated Balance Sheets
Current liability	(17,013)	(17,712)
Noncurrent liability	(149,463)	(171,129)
Funded status	(166,476)	(188,841)
Nonpension postretirement benefit plans \| United States
Projected benefit obligation
Benefit obligation - beginning of year	172,000
Benefit obligation - end of year	$ 154,000	$ 172,000

Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level.

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