Postretirement Plans (Narrative) (Details) (USD $) Share data in Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Postretirement Plans [Line Items]
Accumulated benefit obligation for defined benefit pension plans	$ 35,700,000,000	$ 31,400,000,000
Assets set aside expected to be used to pay obligations of defined benefit pension plans and retiree medical and life insurance plans	29,041,000,000	27,178,000,000
Aggregate liability for postemployment plans	107,000,000	93,000,000
Prior service (credit) cost expected to be recognized in net periodic benefit cost over the next fiscal year	39,000,000
Change in postretirement benefit obligation as a result of increase in one percentage point in the assumed health care cost trend rate	4.40%
Change in postretirement benefit obligation as a result of decrease in one percentage point in the assumed health care cost trend rate	(3.80%)
Change in postretirement service cost plus interest cost as a result of increase in one percentage point in the assumed health care cost trend rate	4.80%
Change in postretirement service cost plus interest cost as a result of decrease in one percentage point in the assumed health care cost trend rate	(3.70%)
Contributions made to defined contribution plans	378,000,000	379,000,000	364,000,000
Shares of our stock held in defined contribution plans we sponsor	52.1	60.7
Non-Qualified Pension Plans [Member]
Postretirement Plans [Line Items]
Benefit plan expense	104,000,000	85,000,000	76,000,000
Non-Qualified Pension Plans, Defined Benefit [Member]
Postretirement Plans [Line Items]
Defined benefit pension plan, liabilities	907,000,000	850,000,000
Unrecognized net actuarial losses	476,000,000	447,000,000
Rabbi Trust [Member]
Postretirement Plans [Line Items]
Assets set aside expected to be used to pay obligations of defined benefit pension plans and retiree medical and life insurance plans	283,000,000	338,000,000
Qualified Defined Benefit Pension Plans [Member]
Postretirement Plans [Line Items]
Assets set aside expected to be used to pay obligations of defined benefit pension plans and retiree medical and life insurance plans	27,292,000,000	25,345,000,000	22,154,000,000
Unrecognized net actuarial losses	15,698,000,000	12,263,000,000
Increase in projected benefit obligations due to a decrease in discount rate	3,800,000,000	1,700,000,000
Prior service (credit) cost expected to be recognized in net periodic benefit cost over the next fiscal year	47,000,000
Contributions made by the employer	2,285,000,000	2,240,000,000
Required qualified defined benefit plans contributions by employer in next fiscal year	1,100,000,000
Retiree Medical And Life Insurance Plans [Member]
Postretirement Plans [Line Items]
Assets set aside expected to be used to pay obligations of defined benefit pension plans and retiree medical and life insurance plans	1,749,000,000	1,833,000,000	1,630,000,000
Unrecognized net actuarial losses	648,000,000	684,000,000
Prior service (credit) cost expected to be recognized in net periodic benefit cost over the next fiscal year	(8,000,000)
Contributions made by the employer		311,000,000
Required qualified defined benefit plans contributions by employer in next fiscal year	$ 112,000,000