Quarterly report pursuant to Section 13 or 15(d)

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

v3.21.2
Share-Based Compensation - Summary of Activity Under Share-Based Compensation Plans (Parenthetical) (Detail) - shares
 9 Months Ended
Sep. 30, 2021
Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Outstanding SARs 800,000  
Number of Shares, Expected to vest [1] 3,212,000  
Market condition awards [Member] | Maximum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Outstanding SARs   100,000
Exercised SARs 100,000  
Performance condition SARs [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Outstanding SARs   1,100,000
Exercised SARs 300,000  
Performance Based Stock Unit Awards [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number of shares, granted during period 447,346  
Number of Shares, Expected to vest 2,988  
Number of Shares, Forfeited 768,754  
Performance Based Stock Unit Awards [Member] | Maximum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number of share based payment awards other than options outstanding and nonvested that can vest maximum 1,156,954 712,596
[1] Includes 768,754 performance-based stock unit awards.