Pension and Other Postretirement Benefits - Changes in Level 3 Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Pension Benefits [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets, January 1	$ 3,665	$ 3,298
Actual return on plan assets [Abstract]
Total actual return on plan assets	488	370
Benefits paid	(262)	(256)
Fair value of plan assets, December 31	4,089	3,665
Pension Benefits [Member] \| Fair Value Inputs Level 3 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets, January 1	1,098	830
Actual return on plan assets [Abstract]
Actual return on plan assets still held at reporting date	84	69
Assets sold during the period	7	0
Total actual return on plan assets	91	69
Purchases, sales, settlements, net	(66)	186
Transfers into (out of) Level 3	(2)	13
Fair value of plan assets, December 31	1,121	1,098
Pension Benefits [Member] \| Fixed Maturities And Equity Securities [Member] \| Fair Value Inputs Level 3 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets, January 1	44	26
Actual return on plan assets [Abstract]
Actual return on plan assets still held at reporting date	0	0
Assets sold during the period	7	0
Total actual return on plan assets	7	0
Purchases, sales, settlements, net	25	5
Transfers into (out of) Level 3	(2)	13
Fair value of plan assets, December 31	74	44
Pension Benefits [Member] \| Real Estate And Mortgage Loans [Member] \| Fair Value Inputs Level 3 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets, January 1	352	303
Actual return on plan assets [Abstract]
Actual return on plan assets still held at reporting date	29	38
Assets sold during the period	0	0
Total actual return on plan assets	29	38
Purchases, sales, settlements, net	(42)	11
Transfers into (out of) Level 3	0	0
Fair value of plan assets, December 31	339	352
Pension Benefits [Member] \| Securities Partnerships [Member]
Actual return on plan assets [Abstract]
Fair value of plan assets, December 31	304	328
Pension Benefits [Member] \| Securities Partnerships [Member] \| Fair Value Inputs Level 3 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets, January 1	328	314
Actual return on plan assets [Abstract]
Actual return on plan assets still held at reporting date	16	18
Assets sold during the period	0	0
Total actual return on plan assets	16	18
Purchases, sales, settlements, net	(40)	(4)
Transfers into (out of) Level 3	0	0
Fair value of plan assets, December 31	304	328
Pension Benefits [Member] \| Hedge Funds [Member]
Actual return on plan assets [Abstract]
Fair value of plan assets, December 31	360	327
Pension Benefits [Member] \| Hedge Funds [Member] \| Fair Value Inputs Level 3 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets, January 1	327	148
Actual return on plan assets [Abstract]
Actual return on plan assets still held at reporting date	38	10
Assets sold during the period	0	0
Total actual return on plan assets	38	10
Purchases, sales, settlements, net	(5)	169
Transfers into (out of) Level 3	0	0
Fair value of plan assets, December 31	360	327
Pension Benefits [Member] \| Guaranteed Deposit Account Contract [Member]
Actual return on plan assets [Abstract]
Fair value of plan assets, December 31	44	47
Pension Benefits [Member] \| Guaranteed Deposit Account Contract [Member] \| Fair Value Inputs Level 3 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets, January 1	47	39
Actual return on plan assets [Abstract]
Actual return on plan assets still held at reporting date	1	3
Assets sold during the period	0	0
Total actual return on plan assets	1	3
Purchases, sales, settlements, net	(4)	5
Transfers into (out of) Level 3	0	0
Fair value of plan assets, December 31	44	47
Other Postretirement Benefits [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets, January 1	20	22
Actual return on plan assets [Abstract]
Total actual return on plan assets	(1)	1
Benefits paid	(3)	(3)
Fair value of plan assets, December 31	16	20
Other Postretirement Benefits [Member] \| Fair Value Inputs Level 3 [Member]
Actual return on plan assets [Abstract]
Total actual return on plan assets	(1)	1
Benefits paid	$ (3)	$ (3)

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 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 2: 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 3: 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 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=21915506&loc=d3e1928-114920

Reference 5: 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 6: 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.

Reference 7: 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.

+ Details

- Definition

The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph a, 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 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Postretirement Benefits

-URI http://asc.fasb.org/extlink&oid=6521376

Reference 3: 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 4: 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 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 60

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Benefits

-URI http://asc.fasb.org/extlink&oid=6506267

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 60

-Glossary Benefits

-URI http://asc.fasb.org/extlink&oid=6506309

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)(6)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)(5)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS106-2

-Paragraph 22

-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

- Definition

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

+ References+ Details