Postretirement Benefit Plans - The Weighted Average Assumptions Used to Determine Net Periodic Benefit Costs (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
United States [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Discount rate	4.39%	4.09%	4.87%
Expected long-term return on plan assets	7.00%	7.50%	7.75%
United Kingdom [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Discount rate	4.00%	3.50%	4.60%
Expected long-term return on plan assets	4.59%	4.66%	5.84%