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
Mar. 31, 2018
Mar. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Realized and unrealized gains (losses) on financial instruments $ 99 $ 175
Fair Value Option Securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Realized and unrealized gains (losses) on financial instruments 114 260
Exchangeable Senior Debentures    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Realized and unrealized gains (losses) on financial instruments 17 (84)
Indemnification Assets    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Realized and unrealized gains (losses) on financial instruments (29)  
Other Financial Instruments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Realized and unrealized gains (losses) on financial instruments $ (3) $ (1)