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Fair Values of Assets and Liabilities - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Fair Value Disclosures [Abstract]      
Carrying value of unfunded commitments, deferred non-yield related loan fees and standby letters of credit $ 774 $ 528  
Other guarantees carrying value 362 200  
Changes to fair value of these MLHFS $ 362 $ 73 $ (60)
Minimum [Member]      
Fair Value Disclosures [Abstract]      
Assumed credit valuation adjustment as percentage of derivative contract fair value 0.00%    
Maximum [Member]      
Fair Value Disclosures [Abstract]      
Assumed credit valuation adjustment as percentage of derivative contract fair value 100.00%    
Weighted Average [Member]      
Fair Value Disclosures [Abstract]      
Assumed credit valuation adjustment as percentage of derivative contract fair value 2.00%