Derivatives And Risk Management (Summary Of Before Tax Effect Of Fair Value Hedges Not Designated For Hedge Accounting) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Basis Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) on Derivatives, Excluding Derivatives, Settled	$ (7)	$ 7
Derivative Instruments, Gain (Loss) on Derivatives, Settled	12	5
Fixed Price Call Options [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) on Derivatives, Excluding Derivatives, Settled	18	(26)
Fixed Price Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) on Derivatives, Excluding Derivatives, Settled	126	37
Derivative Instruments, Gain (Loss) on Derivatives, Settled	(2)
Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) on Derivatives, Excluding Derivatives, Settled	(7)	3
Derivative Instruments, Gain (Loss) on Derivatives, Settled	$ (1)