Retirement Benefits - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) Investment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	$ (17,131)	$ 2,829	$ 9,949
Multi employer pension plan contributions	6,423	6,482	6,715
Defined contribution plans contributions charged to expense	$ 11,800	9,800	$ 9,500
Plan assets held under management by single investment company	99.00%
Number of commingled debt and equity index funds | Investment	6
Number of asset funds individually in excess of ten percent of total plan assets | Investment	4
United States
Defined Benefit Plan Disclosure [Line Items]
Equity securities, target allocation as percentage of total equity securities	85.00%
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Multi Employer Funded Status	65.00%
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligations in excess of plan assets, projected benefit obligation	$ 101,200	71,000
Accumulated benefit obligations in excess of plan assets, accumulated benefit obligation	$ 96,200	$ 66,200
Benefit obligation discount rate	2.10%	1.90%
Benefit obligation rate of compensation increase	3.30%	3.50%
Net periodic benefit cost discount rate	1.90%	2.60%	2.00%
Net periodic benefit cost rate of compensation increase	3.30%	3.50%	3.50%
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation, pension benefit plans	$ 779,100	$ 697,500
Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation discount rate	3.80%	4.40%
Benefit obligation rate of compensation increase	2.60%	2.80%
Net periodic benefit cost discount rate	4.40%	4.70%	4.10%
Net periodic benefit cost rate of compensation increase	2.80%	3.10%	3.00%