Postretirement Healthcare Amount Included in Accumulated Other Comprehensive Income (Detail) - Other Postretirement Plan - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net Actuarial Gain	$ (2.6)	$ (2.4)
Prior Service Cost	0.0	0.0
Gross Amount in Accumulated Other Comprehensive Income	(2.6)	(2.4)
Income Tax Effect	(1.0)	(0.9)
Net Amount in Accumulated Other Comprehensive Income	$ (1.6)	$ (1.5)