Retirement Benefits - Reconciliation of Changes in Benefit Obligations and Fair Value of Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CHANGE IN PLAN ASSETS
Fair value of plan assets at January 1	$ 132,717
Fair value of plan assets at December 31	142,136	$ 132,717
COMPONENTS ON THE CONSOLIDATED BALANCE SHEETS
Other noncurrent assets	93,400
Other noncurrent liabilities	(99,417)	(87,478)
Pension Benefits
CHANGE IN BENEFIT OBLIGATION
Other	0
Pension Benefits | U.S.
CHANGE IN BENEFIT OBLIGATION
Obligation at January 1	95,947	85,175
Service cost	134	653	$ 886
Interest cost	1,274	2,796	2,634
Plan amendments	183	0
Benefits paid	(4,023)	(3,520)
Actuarial loss (gain)	6,504	16,931
Currency translation	0	0
Settlements	(6,064)	(4,826)
Curtailments	0	(1,538)
Acquisition/Divestiture	0	0
Other		276
Obligation at December 31	93,955	95,947	85,175
CHANGE IN PLAN ASSETS
Fair value of plan assets at January 1	93,413	83,580
Actual return on plan assets	16,225	17,446
Employer contributions	421	733
Benefits paid	(4,023)	(3,520)
Currency translation	0	0
Settlements	(6,064)	(4,826)
Acquisition/Divestiture	0	0
Other	0	0
Fair value of plan assets at December 31	99,972	93,413	83,580
Funded status at December 31	6,017	(2,534)
COMPONENTS ON THE CONSOLIDATED BALANCE SHEETS
Other noncurrent assets	10,754	1,921
Current liabilities	(510)	(564)
Other noncurrent liabilities	(4,227)	(3,891)
Net asset (liability) at December 31	6,017	(2,534)
Pension Benefits | Non-U.S.
CHANGE IN BENEFIT OBLIGATION
Obligation at January 1	102,016	89,789
Service cost	2,215	1,844	2,105
Interest cost	1,056	1,440	1,389
Plan amendments	(1)	(156)
Benefits paid	(2,640)	(1,507)
Actuarial loss (gain)	7,279	9,903
Currency translation	8,941	66
Settlements	(3,802)	0
Curtailments	0	0
Acquisition/Divestiture	0	0
Other	624	637
Obligation at December 31	115,688	102,016	89,789
CHANGE IN PLAN ASSETS
Fair value of plan assets at January 1	39,304	33,532
Actual return on plan assets	3,620	3,406
Employer contributions	2,389	2,320
Benefits paid	(2,640)	(1,507)
Currency translation	2,669	916
Settlements	(3,802)	0
Acquisition/Divestiture	0	0
Other	624	637
Fair value of plan assets at December 31	42,164	39,304	33,532
Funded status at December 31	(73,524)	(62,712)
COMPONENTS ON THE CONSOLIDATED BALANCE SHEETS
Other noncurrent assets	3	14
Current liabilities	(1,520)	(1,270)
Other noncurrent liabilities	(72,007)	(61,456)
Net asset (liability) at December 31	(73,524)	(62,712)
Other Benefits
CHANGE IN BENEFIT OBLIGATION
Obligation at January 1	23,257	22,593
Service cost	616	561	668
Interest cost	624	849	810
Plan amendments	(2,905)	0
Benefits paid	(722)	(676)
Actuarial loss (gain)	3,241	(161)
Currency translation	62	91
Settlements	0	0
Curtailments	0	0
Acquisition/Divestiture	0	0
Other	0	0
Obligation at December 31	24,173	23,257	22,593
CHANGE IN PLAN ASSETS
Fair value of plan assets at January 1	0	0
Actual return on plan assets	0	0
Employer contributions	722	676
Benefits paid	(722)	(676)
Currency translation	0	0
Settlements	0	0
Acquisition/Divestiture	0	0
Other	0	0
Fair value of plan assets at December 31	0	0	$ 0
Funded status at December 31	(24,173)	(23,257)
COMPONENTS ON THE CONSOLIDATED BALANCE SHEETS
Other noncurrent assets	0	0
Current liabilities	(990)	(1,127)
Other noncurrent liabilities	(23,183)	(22,130)
Net asset (liability) at December 31	$ (24,173)	$ (23,257)