XML 46 R38.htm IDEA: XBRL DOCUMENT v3.20.1
Summary of Significant Accounting Policies Newly Adopted Accounting Standards (Detail) - USD ($)
$ in Millions
Mar. 31, 2020
Jan. 01, 2020
Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Allowance for credit loss $ 14,073    
Retained earnings 36,552   $ 40,340
Accounting Standards Update 2016-13      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Cumulative Effect of New Accounting Principle in Period of Adoption, Tax   $ 694  
Retained earnings   2,200  
Adjustment amount      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Retained earnings   11  
Allowance for credit losses      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Allowance for credit loss $ 14,073    
Finance charge and fee reserve reclassification   462  
Allowance for credit losses | Accounting Standards Update 2016-13      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Allowance for credit loss   2,900  
Allowance for credit losses | Adjustment amount      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Allowance for credit loss     $ 2,845
Finance charge and fee reserve reclassification   $ 462