Accumulated Other Comprehensive Income (Loss) - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Benefit plans expenses reclassified from accumulated OCI to income	$ 1.3	$ 1.9	$ 3.6	$ 5.6
Deferred gains and losses on derivatives reclassified from accumulated OCI to income	$ 1.1	$ 2.6	$ 5.3	$ 14.9