Quarterly report pursuant to Section 13 or 15(d)

Assets And Liabilities Measured At Fair Value Realized Unrealized Gain Loss (Details)

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Assets And Liabilities Measured At Fair Value Realized Unrealized Gain Loss (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Realized and unrealized gains (losses) on financial instruments $ 20 $ 101 $ 119 $ 276
Fair Value Option Securities        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Realized and unrealized gains (losses) on financial instruments 30 162 144 422
Exchangeable Senior Debentures        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Realized and unrealized gains (losses) on financial instruments 26 (55) 43 (139)
Indemnification Assets        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Realized and unrealized gains (losses) on financial instruments (35)   (64)  
Other Financial Instruments        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Realized and unrealized gains (losses) on financial instruments $ (1) $ (6) $ (4) $ (7)