Reclassifications From Accumulated Other Comprehensive Income (Loss) (Amounts Reclassified From Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
General and administrative expenses	$ 50	$ 54
Provision for income taxes		1
Net Income (Loss)	351	$ (1,132)
Reclassification from Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income (Loss)
Pension And Other Postretirement [Member] | Reclassification from Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
General and administrative expenses	1
Provision for income taxes	1
Net Income (Loss)