Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Increase to liabilities	$ (43)	$ 55
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase to liabilities	250
Employer contributions	6
Pension Plan [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated additional employer contributions	25
Pension Plan [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated additional employer contributions	70
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase to liabilities	$ 70