Other Post-Employment Benefits and Other Employee Benefit Plans - One Percentage Point Change on Assumed Healthcare Cost (Detail) (Other Post-Employment Benefits and Other Employee Benefit Plans [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Other Post-Employment Benefits and Other Employee Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Effect on total of service and interest cost components, 1% Increase	$ 0.1
Effect on post-retirement benefit obligation, 1% Increase	2.2
Effect on total of service and interest cost components, 1% Decrease	(0.1)
Effect on post-retirement benefit obligation, 1% Decrease	$ (2.6)