Derivative Assets And Liabilities Fair Value of Derivative Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Total derivatives assets	$ 243	$ 362
Total derivatives liabilities	(482)	(666)
Designated as Hedging Instrument [Member] | Commodity derivatives (margin deposits)
Total derivatives assets	7	0
Total derivatives liabilities	0	4
Not Designated as Hedging Instrument [Member]
Total derivatives assets	236	362
Total derivatives liabilities	(482)	(662)
Not Designated as Hedging Instrument [Member] | Commodity derivatives (margin deposits)
Total derivatives assets	222	338
Total derivatives liabilities	262	416
Not Designated as Hedging Instrument [Member] | Commodity derivatives
Total derivatives assets	14	24
Total derivatives liabilities	10	52
Not Designated as Hedging Instrument [Member] | Interest rate derivatives
Total derivatives assets	0	0
Total derivatives liabilities	210	193
Embedded Derivatives in Preferred Units [Member] | Not Designated as Hedging Instrument [Member]
Total derivatives assets	0	0
Total derivatives liabilities	$ 0	$ 1