Income Taxes - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - January 1	$ 160.1	$ 161.2	$ 208.8
Additions for:
Prior year tax positions	1.8	2.4	1.6
Current year tax positions	3.4	2.8	8.0
Assumed in acquisition	1.9	0.0	0.0
Reductions for:
Prior year tax positions	(56.6)	(2.8)	(55.4)
Settlements	(19.0)	(1.0)	(1.0)
Lapse of statute	(4.0)	(2.5)	(0.8)
Unrecognized tax benefits - December 31	$ 87.6	$ 160.1	$ 161.2