Annual report pursuant to Section 13 and 15(d)

Summary of Potential Number of Units that Could Vest Under Restricted Stock Unit Awards (Parenthetical) (Detail)

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Summary of Potential Number of Units that Could Vest Under Restricted Stock Unit Awards (Parenthetical) (Detail) - Restricted Stock Units (RSUs) - $ / shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Schedule Of Restricted Stock Unit [Line Items]      
Weighted Average Grant Date Fair Value, Granted $ 36.77   $ 42.37
Minimum      
Schedule Of Restricted Stock Unit [Line Items]      
Weighted Average Grant Date Fair Value, Granted   $ 37.55  
Maximum      
Schedule Of Restricted Stock Unit [Line Items]      
Weighted Average Grant Date Fair Value, Granted   $ 39.03