Income Taxes (Components Of Deferred Tax Balances) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Deferred tax liabilities:
Differences between book and tax basis of property	$ 216	$ 2,504
Derivative activity		122
Other	9	21
Total deferred tax liabilities	225	2,647
Deferred tax assets
Accrued compensation	28	23
Alternative minimum tax credit carryforward	125	131
Accrued pension costs	19	17
Asset retirement obligations	77	79
Net operating loss carryforward	445	323
Other	24	19
Total deferred tax assets	718	592
Valuation allowance	$ (493)	(5)
Net deferred tax liability		$ 2,060