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Stock-Based Compensation - Performance Stock Units Unvested Roll Forward (Detail) - Performance Stock Unit Plan [Member] - $ / shares
shares in Thousands
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unvested Beginning balance, Shares 100    
Shares granted 13 40 40
Shares Forfeited (8)    
Unvested Ending balance, Shares 105 100  
Weighted-average grant date fair value per share of shares unvested at beginning of period $ 212.34    
Weighted-average grant date fair value per share of shares granted 372.68    
Weighted-average grant date fair value per share of shares forfeited 200.26    
Weighted-average grant date fair value per share of shares unvested at end of period $ 233.11 $ 212.34