Pension Plans, Retirement Benefits and Savings Plans (details) - Fair Value Hierarchy (Pension Plans [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined benefit plan disclosure
Fair value of plan assets	$ 2,859	$ 2,500	$ 2,425
Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	2,170	1,945
Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	683	537
Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	6	18
Fixed maturities [Member]
Defined benefit plan disclosure
Fair value of plan assets	413	256
Fixed maturities [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets		15
Fixed maturities [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	413	239
Fixed maturities [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets		2
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Defined benefit plan disclosure
Fair value of plan assets		15
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets		15
Obligations of states, municipalities and political subdivisions [Member]
Defined benefit plan disclosure
Fair value of plan assets	7
Obligations of states, municipalities and political subdivisions [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	7
Debt securities issued by foreign governments [Member]
Defined benefit plan disclosure
Fair value of plan assets	14	13
Debt securities issued by foreign governments [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	14	13
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Defined benefit plan disclosure
Fair value of plan assets	9	14
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	9	12
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets		2
All other corporate bonds [Member]
Defined benefit plan disclosure
Fair value of plan assets	383	214
All other corporate bonds [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	383	214
Total mutual funds [Member]
Defined benefit plan disclosure
Fair value of plan assets	1,549	1,375
Total mutual funds [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	1,549	1,375
Equity mutual funds [Member]
Defined benefit plan disclosure
Fair value of plan assets	1,143	932
Equity mutual funds [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	1,143	932
Bond mutual funds [Member]
Defined benefit plan disclosure
Fair value of plan assets	406	443
Bond mutual funds [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	406	443
Equity securities [Member]
Defined benefit plan disclosure
Fair value of plan assets	450	352
Equity securities [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	450	352
Other investments [Member]
Defined benefit plan disclosure
Fair value of plan assets	6	16
Other investments [Member] | Level 3 [Member]
Defined benefit plan disclosure
Fair value of plan assets	6	16
Cash and short-term securities [Member]
Defined benefit plan disclosure
Fair value of plan assets	441	501
Cash and short-term securities [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	171	203
Cash and short-term securities [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	270	298
Cash and short-term securities, U.S. Treasury securities [Member]
Defined benefit plan disclosure
Fair value of plan assets	132	141
Cash and short-term securities, U.S. Treasury securities [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	132	141
Money market mutual funds [Member]
Defined benefit plan disclosure
Fair value of plan assets	22	50
Money market mutual funds [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	22	50
Cash and short-term securities, other [Member]
Defined benefit plan disclosure
Fair value of plan assets	287	310
Cash and short-term securities, other [Member] | Level 1 [Member]
Defined benefit plan disclosure
Fair value of plan assets	17	12
Cash and short-term securities, other [Member] | Level 2 [Member]
Defined benefit plan disclosure
Fair value of plan assets	$ 270	$ 298