Accumulated Other Comprehensive Income (Loss) - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Benefit plans expenses reclassified from accumulated OCI to income	$ 1.7	$ 1.1	$ 3.4	$ 2.3
Gain/(Loss), Reclassified from AOCI to Income	$ 11.2	$ 2.2	$ 18.6	$ 4.2