Accumulated Other Comprehensive Income Reclassifications out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		$ (1,633)	$ (1,839)	$ (4,129)	$ (5,047)
Tax (expense)/benefit		613	683	1,553	1,883
Net of tax		(1,020)	(1,156)	(2,576)	(3,164)
Pension and Retiree Health and Welfare Benefit Items [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Actuarial losses	[1],[2]	0	(1)	0	(3)
Prior service credits	[1],[2]	1	1	2	2
Total before tax	[1]	1	0	2	(1)
Tax (expense)/benefit	[1]	0	0	(1)	1
Net of tax	[1]	$ 1	$ 0	$ 1	$ 0

[1] Amounts in parenthesis indicate debits to the income statement.

[2] This accumulated other comprehensive income component is included in the computation of net periodic pension and retiree health and welfare cost (see Note 8 for additional details).