Retirement Plans (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 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	$ 15	$ 11
Pension/OPEB costs	(3)	$ (21)	$ 74
Plan assets	1,576		$ 1,673
Defined Benefit Plan, Fair Value of Plan Assets, Period Increase (Decrease)	$ (97)
Percentage of increase in pension plan	(6.00%)
Asset plan transfers	$ 5
Defined benefit plan, cash contributions by employer	62
Benefit payments	104
Negative investment returns	60
Minimum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated Pension And OPEB Expense	90
Maximum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated Pension And OPEB Expense	$ 100