Fair Values of Financial Instruments (Details 2) (Pension Benefits [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	$ 2,001	$ 1,922
Level 1 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	357	363
Level 2 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	1,620	1,540
Level 3 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	24	19
Other assets [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	47	39
Other assets [Member] | Level 1 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	21	15
Other assets [Member] | Level 2 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	8	6
Other assets [Member] | Level 3 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	18	18
Short term investments [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	45	64
Short term investments [Member] | Level 1 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	0	0
Short term investments [Member] | Level 2 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	45	64
Short term investments [Member] | Level 3 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	0	0
Fixed Maturities [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	735	638
Fixed Maturities [Member] | Level 1 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	0	0
Fixed Maturities [Member] | Level 2 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	729	637
Fixed Maturities [Member] | Level 3 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	6	1
Fixed Maturities [Member] | U.S. Government and government agency and authority obligations [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	207	168
Fixed Maturities [Member] | U.S. Government and government agency and authority obligations [Member] | Level 1 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	0	0
Fixed Maturities [Member] | U.S. Government and government agency and authority obligations [Member] | Level 2 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	204	167
Fixed Maturities [Member] | U.S. Government and government agency and authority obligations [Member] | Level 3 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	3	1
Fixed Maturities [Member] | Corporate bonds [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	290	272
Fixed Maturities [Member] | Corporate bonds [Member] | Level 1 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	0	0
Fixed Maturities [Member] | Corporate bonds [Member] | Level 2 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	289	272
Fixed Maturities [Member] | Corporate bonds [Member] | Level 3 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	1	0
Fixed Maturities [Member] | Foreign government and government agency obligations [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	62	41
Fixed Maturities [Member] | Foreign government and government agency obligations [Member] | Level 1 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	0	0
Fixed Maturities [Member] | Foreign government and government agency obligations [Member] | Level 2 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	61	41
Fixed Maturities [Member] | Foreign government and government agency obligations [Member] | Level 3 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	1	0
Fixed Maturities [Member] | Mortgage-backed securities [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	176	157
Fixed Maturities [Member] | Mortgage-backed securities [Member] | Level 1 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	0	0
Fixed Maturities [Member] | Mortgage-backed securities [Member] | Level 2 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	175	157
Fixed Maturities [Member] | Mortgage-backed securities [Member] | Level 3 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	1	0
Equity securities [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	1,174	1,181
Equity securities [Member] | Level 1 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	336	348
Equity securities [Member] | Level 2 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	838	833
Equity securities [Member] | Level 3 [Member]
Fair values of the pension plan assets categorized based upon the lowest level of input [Abstract]
Plan assets at fair value	$ 0	$ 0