Assets And Liabilities Measured At Fair Value Realized Unrealized Gain Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Realized and unrealized gains (losses) on financial instruments, net	$ 114	$ (57)	$ (22)
Fair Value Option Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Realized and unrealized gains (losses) on financial instruments, net	84	173	514
Exchangeable Senior Debentures
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Realized and unrealized gains (losses) on financial instruments, net	$ 30	$ (230)	(553)
Other Financial Instruments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Realized and unrealized gains (losses) on financial instruments, net			$ 17