Retirement Benefits - Changes in Benefit Obligations and Plan Assets as Well as Funded Status of Retirement Plans (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) Investment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Domestic Pension Plans, Funded Percentage	112.00%	117.00%
Number Of Indexed Funds | Investment	6
Change in plan assets
Fair value of plan assets at beginning of year	$ 825,806
Fair value of plan assets at end of year	732,502	$ 825,806
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation	93,100	96,200
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation	95,600	101,200
Pension Plan [Member]
Change in benefit obligation [Roll Forward]
Obligation at beginning of year	808,149	726,421
Service cost	14,238	13,372	$ 12,895
Interest cost	25,316	25,501	25,781
Actuarial (gains) losses	(53,044)	54,562
Acquisition	0	19,225
Special termination benefits	0	0	2,837
Plan amendments	0	147
Benefits paid	(38,335)	(43,598)
Participant contributions	0	0
Foreign currency exchange rate changes	(4,699)	12,519
Obligation at end of year	751,625	808,149	726,421
Change in plan assets
Fair value of plan assets at beginning of year	825,806	759,551
Actual return on plan assets	(57,082)	108,154
Employer contributions	2,113	1,699
Participant contributions	0	0
Benefits paid	(38,335)	(43,598)
Fair value of plan assets at end of year	732,502	825,806	759,551
Funded status	(19,123)	17,657
Amounts recognized in the consolidated balance sheets
Non-current assets	76,443	118,892
Current liabilities	(2,174)	(2,227)
Non-current liabilities	(93,392)	(99,008)
Net amount recognized	(19,123)	17,657
Amounts recognized in accumulated other comprehensive loss (income)
Net actuarial loss (gain)	218,867	154,642
Prior service cost (credit)	765	938
Net amount recognized	219,632	155,580
Other Postretirement Benefits Plan [Member]
Change in benefit obligation [Roll Forward]
Obligation at beginning of year	20,939	21,698
Service cost	99	104	222
Interest cost	640	692	891
Actuarial (gains) losses	(2,031)	630
Acquisition	0	0
Plan amendments	1,210	(2)
Benefits paid	(1,764)	(2,325)
Participant contributions	93	142
Foreign currency exchange rate changes	0	0
Obligation at end of year	19,186	20,939	21,698
Change in plan assets
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	1,671	2,183
Participant contributions	93	142
Benefits paid	(1,764)	(2,325)
Fair value of plan assets at end of year	0	0	$ 0
Funded status	(19,186)	(20,939)
Amounts recognized in the consolidated balance sheets
Non-current assets	0	0
Current liabilities	(1,924)	(2,083)
Non-current liabilities	(17,262)	(18,856)
Net amount recognized	(19,186)	(20,939)
Amounts recognized in accumulated other comprehensive loss (income)
Net actuarial loss (gain)	(7,087)	(5,561)
Prior service cost (credit)	(8,735)	(11,337)
Net amount recognized	$ (15,822)	$ (16,898)