Retirement Plans (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Capitalization of pension and OPEB expense related to engineering and plant construction	$ 10	$ 8
Pension/OPEB costs			$ 74
Plan assets	1,659		$ 1,673
Defined Benefit Plan, Fair Value of Plan Assets, Period Increase (Decrease)	$ 14
Percentage of increase in pension plan	1.00%
Defined benefit plan, cash contributions by employer	$ 40
Benefit payments	60
Positive investment returns	6
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year	100
Minimum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated Pension And OPEB Expense	85
Maximum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated Pension And OPEB Expense	$ 105