Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation - Summary of Activity Under Share-Based Compensation Plans (Detail)

v3.8.0.1
Share-Based Compensation - Summary of Activity Under Share-Based Compensation Plans (Detail) - USD ($)
$ / shares in Units, shares in Thousands, $ in Millions
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
SARs [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Awards Outstanding, Beginning Balance     11,998    
Granted, Awards     1,358    
Exercised, Awards     (2,511)    
Forfeited, Awards     (321)    
Awards Outstanding, Ending Balance 10,524   10,524   11,998
Exercisable Awards, Ending Balance 6,308   6,308    
Weighted Average Exercise Price Outstanding, Beginning Balance     $ 41.52    
Granted, Weighted Average Exercise Price     57.30    
Exercised, Weighted Average Exercise Price     28.62    
Forfeited, Weighted Average Exercise Price     53.67    
Weighted Average Exercise Price Outstanding, Ending Balance $ 46.26   46.26   $ 41.52
Exercisable, Weighted Average Exercise Price, Ending Balance $ 45.61   $ 45.61    
Weighted Average Remaining Contractual Term Outstanding     6 years 3 months 19 days   6 years
Exercisable Weighted Average Remaining Contractual Term     4 years 10 months 25 days    
Aggregate Intrinsic Value Outstanding $ 237.4   $ 237.4   $ 148.7
Exercisable, Aggregate Intrinsic Value $ 150.6   $ 150.6    
Granted, Weighted Average Grant Date Fair Value $ 31.31 $ 32.06 $ 28.36 $ 29.49  
Incentive Plan and Independent Directors Stock Units [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Outstanding and nonvested December 31, 2016, Shares     26    
Granted, Shares     154    
Vested, Shares     (24)    
Outstanding and nonvested September 30, 2017, Shares 156   156   26
Outstanding and nonvested December 31, 2016, Weighted Average Grant Date Fair Value     $ 62.35    
Granted, Weighted Average Grant Date Fair Value     68.84    
Vested, Weighted Average Grant Date Fair Value     62.42    
Outstanding and nonvested September 30, 2017, Weighted Average Grant Date Fair Value $ 68.77   $ 68.77   $ 62.35