v3.20.4
Loans - Loans, Level 3 Rollforward (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Loans Receivable [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, Beginning Balance $ 1,890 $ 1,990
Net realized gains / (losses) 72 46
Net unrealized gains/(losses) 87 85
Purchases 670 249
Sales (50) (14)
Settlements (727) (795)
Transfers into level 3 836 444
Transfers out of level 3 (100) (115)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, Ending Balance 2,678 1,890
Corporate [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, Beginning Balance 752 659
Net realized gains / (losses) 22 5
Net unrealized gains/(losses) (22) (27)
Purchases 277 151
Sales (38)  
Settlements (125) (298)
Transfers into level 3 163 290
Transfers out of level 3 (100) (28)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, Ending Balance 929 752
Commercial real estate [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, Beginning Balance 591 677
Net realized gains / (losses) 24 20
Net unrealized gains/(losses) 60 28
Purchases 334 11
Sales (5) (9)
Settlements (366) (229)
Transfers into level 3 466 94
Transfers out of level 3   (1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, Ending Balance 1,104 591
Residential real estate [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, Beginning Balance 221 290
Net realized gains / (losses) 13 15
Net unrealized gains/(losses) 10 26
Purchases 48 58
Sales (2) (5)
Settlements (78) (137)
Transfers into level 3 48 60
Transfers out of level 3   (86)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, Ending Balance 260 221
Wealth management and other [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, Beginning Balance 326 364
Net realized gains / (losses) 13 6
Net unrealized gains/(losses) 39 58
Purchases 11 29
Sales (5)  
Settlements (158) (131)
Transfers into level 3 159  
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value, Ending Balance $ 385 $ 326