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, $ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Outstanding and nonvested as of December 31, 2017, Number of Shares 163,000  
Granted, Number of Shares 662,000  
Vested, Number of Shares (1,000)  
Forfeited, Number of Shares (6,000)  
Outstanding and nonvested as of March 31, 2018, Number of Shares 818,000 163,000
Outstanding and nonvested as of December 31, 2017, Weighted Average Grant Date Fair Value Per Share $ 68.69  
Granted, Weighted Average Grant Date Fair Value Per Share 86.30  
Vested, Weighted Average Grant Date Fair Value Per Share 61.14  
Forfeited, Weighted Average Grant Date Fair Value Per Share 86.30  
Outstanding and nonvested as of March 31, 2018, Weighted Average Grant Date Fair Value Per Share $ 82.81 $ 68.69
SARs [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number of Awards Outstanding, Beginning Balance 9,597,000  
Granted, Number of Awards 0  
Exercised, Number of Awards (2,379,000)  
Forfeited, Number of Awards (81,000)  
Number of Awards Outstanding, Ending Balance 7,137,000 9,597,000
Number of Awards Exercisable, Ending Balance 4,992,000  
Weighted Average Exercise Price Per Award Outstanding, Beginning Balance $ 46.72  
Exercised, Weighted Average Exercise Price Per Award 40.49  
Forfeited, Weighted Average Exercise Price Per Award 55.92  
Weighted Average Exercise Price Per Award Outstanding, Ending Balance 48.69 $ 46.72
Exercisable, Weighted Average Exercise Price Per Award, Ending Balance $ 44.32  
Weighted Average Remaining Contractual Term Outstanding 6 years 2 months 12 days 6 years 2 months 12 days
Exercisable Weighted Average Remaining Contractual Term 5 years 3 months 18 days  
Aggregate Intrinsic Value Outstanding $ 348.1 $ 212.0
Exercisable, Aggregate Intrinsic Value $ 265.3  
Granted, Weighted Average Grant Date Fair Value Per Share   $ 28.32