Income Taxes - Unrecognized Tax Benefits and Effect on Effective Income Tax Rate (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Beginning balance of unrecognized tax benefits	$ 188.9	$ 221.9	$ 233.2
Additions for tax positions of current year	3.1	5.2	7.5
Additions for tax positions of prior years	111.9	7.7	5.0
Reductions for tax positions of prior years	(64.8)	(45.9)	(23.8)
Ending balance of unrecognized tax benefits	$ 239.1	$ 188.9	$ 221.9