Accumulated Other Comprehensive Income (Loss) - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Benefit plans expenses reclassified from accumulated OCI to income	$ 1.7	$ 1.3	$ 5.0	$ 3.6
Gain/(Loss), Reclassified from AOCI to Income	$ 7.4	$ 1.1	$ 26.0	$ 5.3