Benefit Plans (Postretirement Health Care Costs) (Details) - Other Postretirement Benefit Plan, Defined Benefit [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5	$ 4	$ 9	$ 8
Interest cost	25	27	51	54
Amortization of net loss	11	7	23	14
Amortization of prior service credit	(10)	(10)	(20)	(21)
Net Periodic Benefit Cost	$ 31	$ 28	$ 63	$ 55