Share-Based Compensation Expense, Number of Deferred Stock Units Granted, Weighted Average Grant-Date Fair Value, and Aggregate Intrinsic Value of Non-Employee Director Deferred Stock Units (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Share-based compensation expense (in millions)	$ 113.0	$ 109.0	$ 116.0
Deferred Stock Units | Director
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Share-based compensation expense (in millions)	$ 1.1	$ 1.2	$ 1.4
Non-employee director deferred stock units granted	15,000	21,000	31,000
Weighted average grant-date fair value (per share)	$ 80	$ 59	$ 44
Aggregate intrinsic value of shares distributed (in millions)	$ 1.8	$ 0.8	$ 0.7