Retirement Benefits - Reconciliation Of Changes In Benefit Obligations And Fair Value Of Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CHANGE IN PLAN ASSETS
Fair value of plan assets at January 1	$ 106,274
Fair value of plan assets at December 31	112,505	$ 106,274
Other noncurrent liabilities	(99,646)	(93,604)
Pension Benefit Plan
CHANGE IN BENEFIT OBLIGATION
Other	0
Pension Benefit Plan | U.S. Plans
CHANGE IN BENEFIT OBLIGATION
Obligation at January 1	90,256	98,476
Service cost	976	1,016	$ 1,279
Interest cost	2,677	3,043	3,770
Plan amendments	0	0
Benefits paid	(6,258)	(3,140)
Actuarial loss (gain)	3,684	1,987
Currency translation	0	0
Settlements	0	(11,126)
Acquisition/Divestiture	0	0
Other		0
Obligation at December 31	91,335	90,256	98,476
CHANGE IN PLAN ASSETS
Fair value of plan assets at January 1	73,688	77,575
Actual return on plan assets	5,046	6,740
Employer contributions	3,565	3,639
Benefits paid	(6,258)	(3,140)
Currency translation	0	0
Settlements	0	(11,126)
Acquisition/Divestiture	0	0
Other	0	0
Fair value of plan assets at December 31	76,041	73,688	77,575
Funded status at December 31	(15,294)	(16,568)
Current liabilities	(658)	(729)
Other noncurrent liabilities	(14,636)	(15,839)
Net liability at December 31	(15,294)	(16,568)
Pension Benefit Plan | Non-U.S. Plans
CHANGE IN BENEFIT OBLIGATION
Obligation at January 1	87,764	58,063
Service cost	1,975	1,627	1,506
Interest cost	1,283	1,429	1,734
Plan amendments	0	0
Benefits paid	(1,942)	(2,023)
Actuarial loss (gain)	(15)	6,844
Currency translation	9,323	(6,988)
Settlements	(2,452)	(819)
Acquisition/Divestiture		29,491
Acquisition/Divestiture	(482)
Other	1,997	140
Obligation at December 31	97,451	87,764	58,063
CHANGE IN PLAN ASSETS
Fair value of plan assets at January 1	32,586	20,645
Actual return on plan assets	1,792	2,470
Employer contributions	2,702	1,974
Benefits paid	(1,942)	(2,023)
Currency translation	2,446	(4,108)
Settlements	(2,452)	(819)
Acquisition/Divestiture	0	14,307
Other	1,184	140
Fair value of plan assets at December 31	36,316	32,586	20,645
Funded status at December 31	(61,135)	(55,178)
Current liabilities	(1,159)	(1,005)
Other noncurrent liabilities	(59,976)	(54,173)
Net liability at December 31	(61,135)	(55,178)
Other Benefit Plans
CHANGE IN BENEFIT OBLIGATION
Obligation at January 1	24,636	20,400
Service cost	610	601	673
Interest cost	818	811	833
Plan amendments	0	0
Benefits paid	(738)	(718)
Actuarial loss (gain)	592	(1,990)
Currency translation	150	52
Settlements	0	0
Acquisition/Divestiture	0	5,480
Other	0	0
Obligation at December 31	26,068	24,636	20,400
CHANGE IN PLAN ASSETS
Fair value of plan assets at January 1	0	0
Actual return on plan assets	0	0
Employer contributions	738	718
Benefits paid	(738)	(718)
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	(26,068)	(24,636)
Current liabilities	(1,034)	(1,044)
Other noncurrent liabilities	(25,034)	(23,592)
Net liability at December 31	$ (26,068)	$ (24,636)