Pension and Other Employee Benefits - Discount Rate Used in Computation of Respective Benefit Obligations (Detail) - Pension Benefits [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
US Pension Benefits [Member]
Pension Plans Postretirement And Other Employee Benefits [Line Items]
Discount rate used in benefit obligation	3.30%	3.80%
Non US Pension Benefits [Member]
Pension Plans Postretirement And Other Employee Benefits [Line Items]
Discount rate used in benefit obligation	1.76%	1.75%