Retirement Benefits (Details 12) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010
Pension Plans Defined Benefit [Member]
Changes in fair value measurement of level three items in pension plan assets
Fair value of plan assets beginning of year	$ 6,822
Actual return on investments:
Total return on investments	256	859
Fair value of plan assets end of year	6,722	6,822
Pension Plans Defined Benefit [Member] \| Real estate investments [Member]
Actual return on investments:
Fair value of plan assets end of year	1,002	858
Pension Plans Defined Benefit [Member] \| Private equity [Member]
Actual return on investments:
Fair value of plan assets end of year	582	638
Other Postretirement Benefits [Member]
Changes in fair value measurement of level three items in pension plan assets
Fair value of plan assets beginning of year	790
Actual return on investments:
Total return on investments	4	82
Fair value of plan assets end of year	786	790
Other Postretirement Benefits [Member] \| Real estate investments [Member]
Actual return on investments:
Fair value of plan assets end of year	39	33
Other Postretirement Benefits [Member] \| Private equity [Member]
Actual return on investments:
Fair value of plan assets end of year	23	23
Significant Unobservable Inputs (Level 3) [Member] \| Pension Plans Defined Benefit [Member]
Actual return on investments:
Fair value of plan assets end of year	1,367	1,315
Significant Unobservable Inputs (Level 3) [Member] \| Pension Plans Defined Benefit [Member] \| Real estate investments [Member]
Changes in fair value measurement of level three items in pension plan assets
Fair value of plan assets beginning of year	674	547
Actual return on investments:
Related to investments held at year end	72	59
Related to investments sold during the year	20	18
Total return on investments	92	77
Purchases, sales, and settlements	16	50
Transfers into/out of Level 3
Fair value of plan assets end of year	782	674
Significant Unobservable Inputs (Level 3) [Member] \| Pension Plans Defined Benefit [Member] \| Private equity [Member]
Changes in fair value measurement of level three items in pension plan assets
Fair value of plan assets beginning of year	638	555
Actual return on investments:
Related to investments held at year end	(12)	67
Related to investments sold during the year	47	18
Total return on investments	35	85
Purchases, sales, and settlements	(91)	(2)
Transfers into/out of Level 3
Fair value of plan assets end of year	582	638
Significant Unobservable Inputs (Level 3) [Member] \| Other Postretirement Benefits [Member]
Actual return on investments:
Fair value of plan assets end of year	53	49
Significant Unobservable Inputs (Level 3) [Member] \| Other Postretirement Benefits [Member] \| Real estate investments [Member]
Changes in fair value measurement of level three items in pension plan assets
Fair value of plan assets beginning of year	26	24
Actual return on investments:
Related to investments held at year end	3	2
Related to investments sold during the year	1
Total return on investments	4	2
Transfers into/out of Level 3
Fair value of plan assets end of year	30	26
Significant Unobservable Inputs (Level 3) [Member] \| Other Postretirement Benefits [Member] \| Private equity [Member]
Changes in fair value measurement of level three items in pension plan assets
Fair value of plan assets beginning of year	23	24
Actual return on investments:
Related to investments held at year end		1
Related to investments sold during the year	2
Total return on investments	2	1
Purchases, sales, and settlements	(2)	(2)
Transfers into/out of Level 3
Fair value of plan assets end of year	$ 23	$ 23

The difference between fair value of plan assets at the end of the period and the fair value at the beginning of the period, adjusted for contributions and payments of benefits during the period, and after adjusting for taxes and other expenses, as applicable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Actual Return on Plan Assets (Component of Net Periodic Pension Cost)

-URI http://asc.fasb.org/extlink&oid=6504226

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Actual Return on Plan Assets (Component of Net Periodic Postretirement Benefit Cost)

-URI http://asc.fasb.org/extlink&oid=6504192

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)(1)

-URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 106

-Paragraph 518

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 87

-Paragraph 264

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph d(iv)(b)(i)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details