Benefit Obligations (Schedule of Expense Related to Nonqualified Pension Plans Included in Net Periodic Benefit Cost, Excluding Returns on Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Nonqualified Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	$ 18	$ 0	[1]	$ 43

[1] Actuarial gain offset interest cost.