XML 112 R88.htm IDEA: XBRL DOCUMENT v3.20.4
Schedule II - Valuation and Qualifying Accounts (Details) - UAL and United - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Allowance for doubtful accounts      
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Period $ 9 $ 8 $ 7
Additions Charged to Costs and Expenses 70 17 17
Deductions 16 16 16
Other 15 0 0
Balance at End of Period 78 9 8
Obsolescence allowance-spare parts      
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Period 425 412 354
Additions Charged to Costs and Expenses 88 76 73
Deductions 35 63 15
Other 0 0 0
Balance at End of Period 478 425 412
Allowance for credit losses - notes receivable      
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Period 0    
Additions Charged to Costs and Expenses 518    
Deductions 0    
Other 4    
Balance at End of Period 522 0  
Valuation allowance for deferred tax assets      
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Period 58 59 63
Additions Charged to Costs and Expenses 197 0 2
Deductions 8 1 6
Other 0 0 0
Balance at End of Period $ 247 $ 58 $ 59