Income Taxes - Reconciliation of the Beginning and Ending Amount of Unrecognized Tax Benefits, Exclusive of Penalties and Interest (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1	$ 13.8	$ 9.3
Additions based on tax positions related to current year	0.0	3.7
(Reductions) additions for tax positions of prior years	(0.6)	3.3
Reductions due to lapse of statute of limitations	0.0	(2.5)
Balance at December 31	$ 13.2	$ 13.8