Stockholders' Equity Stockholder's Equity (Schedule of tax benefit (expense) on net activity) (Details) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Other Comprehensive Income (Loss), Tax	$ (61)	$ 402
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Other Comprehensive Income (Loss), Tax	1	(10)
Pension Plan [Member]
Other Comprehensive Income (Loss), Tax	(60)	351
Other Post Employment Benefit Plans [Member]
Other Comprehensive Income (Loss), Tax	$ (2)	$ 61

Amount of tax expense (benefit) allocated to other comprehensive income (loss).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e640-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 20
-Section 45
-Paragraph 11
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65896914&loc=d3e39076-109324

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration