Quarterly report pursuant to Section 13 or 15(d)

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

v3.20.2
Share-Based Compensation - Summary of Activity Under Share-Based Compensation Plans (Detail) - USD ($)
$ / shares in Units, $ in Millions
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Outstanding and nonvested as of December 31, 2019, Number of Shares     1,833,000    
Granted, Number of Shares     1,975,000    
Vested, Number of Shares     (321,000)    
Forfeited, Number of Shares     (115,000)    
Outstanding and nonvested as of September 30, 2020, Number of Shares 3,372,000   3,372,000   1,833,000
Number of Shares, Expected to vest as of September 30, 2020 3,094,000   3,094,000    
Outstanding and nonvested as of December 31, 2019, Weighted Average Grant Date Fair Value Per Share     $ 49.49    
Granted, Weighted Average Grant Date Fair Value Per Share     39.63    
Vested, Weighted Average Grant Date Fair Value Per Share     49.32    
Forfeited, Weighted Average Grant Date Fair Value Per Share     43.94    
Outstanding and nonvested as of September 30, 2020, Weighted Average Grant Date Fair Value Per Share $ 43.92   43.92   $ 49.49
Expected to vest as of September 30, 2020, Weighted Average Grant Date Fair Value Per Share $ 43.61   $ 43.61    
SARs [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of Awards Outstanding, Beginning Balance     7,001,000    
Granted, Number of Awards 0 0 0 0  
Exercised, Number of Awards     (2,914,000)    
Forfeited, Number of Awards     (7,000)    
Number of Awards Outstanding, Ending Balance 4,080,000   4,080,000   7,001,000
Number of Awards Exercisable, Ending Balance 4,074,000   4,074,000    
Number of Awards Vested and expected to vest, Ending Balance 4,080,000   4,080,000    
Weighted Average Exercise Price Per Award Outstanding, Beginning Balance     $ 27.85    
Exercised, Weighted Average Exercise Price Per Award     28.46    
Forfeited, Weighted Average Exercise Price Per Award     29.03    
Weighted Average Exercise Price Per Award Outstanding, Ending Balance $ 27.41   27.41   $ 27.85
Exercisable, Weighted Average Exercise Price Per Award, Ending Balance 27.41   27.41    
Weighted Average Exercise Price Per Award, Vested and expected to vest, Ending Balance $ 27.41   $ 27.41    
Weighted Average Remaining Contractual Term Outstanding     4 years 8 months 12 days   5 years 4 months 24 days
Exercisable Weighted Average Remaining Contractual Term     4 years 8 months 12 days    
Weighted Average Remaining Contractual Term, Vested and expected to vest     4 years 8 months 12 days    
Aggregate Intrinsic Value Outstanding $ 78.5   $ 78.5   $ 138.7
Exercisable, Aggregate Intrinsic Value 78.4   78.4    
Aggregate Intrinsic Value, Vested and expected to vest $ 78.5   $ 78.5