Significant Weighted Average Assumptions Used in Measurement of OPEB Obligations (Detail) (Foreign Postretirement Benefit Plan [Member])	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Foreign Postretirement Benefit Plan [Member]
OPEB benefit obligations:
Discount rate	3.84%	4.65%	3.90%
Net periodic benefit cost:
Discount rate	4.65%	3.90%	4.18%
Initial health care costs trend rate	5.91%	6.11%	6.40%
Ultimate health care costs trend rate	5.02%	5.03%	5.02%
Year ultimate reached	2018	2018	2018