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Reconciliation of Effective Tax Rate to Federal Statutory Tax Rate (Detail)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Income Tax Disclosure [Abstract]      
U.S. federal statutory rate 21.00% 21.00% 34.90%
Federal tax law changes (0.00%) 0.50% (112.20%)
State taxes, net of federal benefit 3.50% 3.70% 2.80%
Federal and state incentives (0.90%) (0.90%) (7.00%)
State law changes 0.70%   2.00%
Permanent differences 1.20% 0.60% 0.20%
Net effective rate 25.50% 24.90% (79.30%)