Employee Benefit Plans (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Percentage of bonds with highest yields excluded from calculation of yield curve for pension plan assumptions	10.00%
Percentage of bonds with lowest yields excluded from calculation of yield curve for pension plan assumptions	40.00%
Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets	6.75%	7.00%	7.50%
Defined Contribution Plan Employer Matching Contribution Percentage	4.00%
ERRP Reimbursement Funding	$ 5,000,000,000
Minimum Matching Employer Contribution	2,000
Defined Contribution Plan Employee benefit plan expense	$ 126,000,000	$ 108,000,000	$ 120,000,000
Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets 2015	6.75%
Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Fixed earnings credit given to all new participants in pension and postretirement plans	3.00%
Employer contribution	$ 200,000,000
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Employer contribution	222,000,000	$ 21,000,000
Postretirement Benefits | VEBA Contribution
Defined Benefit Plan Disclosure [Line Items]
Employer contribution	$ 200,000,000
Equity Securities [Member] | Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of the fair value of total Plan assets held	70%
Fixed Income Securities | Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of the fair value of total Plan assets held	21%
Real Estate | Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of the fair value of total Plan assets held	5%
Employee Benefit Plans Other Assets [Member] | Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of the fair value of total Plan assets held	4%