XML 35 R25.htm IDEA: XBRL DOCUMENT v3.21.1
Coronavirus Pandemic ("COVID-19") - Additional Information (Detail) - COVID-19 [Member] - USD ($)
 3 Months Ended
Mar. 31, 2021
Dec. 31, 2020
Mar. 27, 2020
Reimbursement of Lost Revenue     $ 100,000,000,000
Proceeds From Contribution In Aid Of Reimbursement of Lost Revenue $ 7.7 $ 22,000,000.0  
2020 Tax Year [Member]      
Percentage of refund of income tax at the prior period corporate tax rate 35.00%    
Rural Area [Member]      
Reimbursement of Lost Revenue     $ 70,000,000,000
Executive Officer [Member]      
Decrease In Salary | % 50.00%