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Stock Benefit Plans - Additional Information (Detail)
Dec. 31, 2019
shares
2010 Incentive Plan [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Common stock reserved for issuance 23,390,511
Shares available for issuance 16,079,083
Directors' Plan [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Common stock reserved for issuance 4,333,939
Shares available for issuance 2,176,642