Retirement Benefits - Weighted Average Actuarial Assumptions to Determine Net Period Cost (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.80%	4.40%	4.70%
Expected return on plan assets	8.50%	8.50%	8.50%
Rate of compensation increase	2.60%	2.80%	3.10%
Health care cost trend rate	6.20%	6.40%	6.60%
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.10%	1.90%	2.60%
Rate of compensation increase	3.30%	3.30%	3.50%