Employee Benefit Plans (Details 13) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
United States Pension Plans of US Entity, Defined Benefit [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at beginning of year	$ 7,108	$ 6,310
Purchases, Sales, Issuances and Settlements	0	0
Fair value of plan assets at end of year	7,879	7,108
United States Pension Plans of US Entity, Defined Benefit [Member] | Corporate fixed maturity securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	2,279	1,964
United States Pension Plans of US Entity, Defined Benefit [Member] | State and political subdivision securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	258	184
United States Pension Plans of US Entity, Defined Benefit [Member] | Foreign government debt securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	769	218
United States Pension Plans of US Entity, Defined Benefit [Member] | Other Debt Securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	497	475
United States Pension Plans of US Entity, Defined Benefit [Member] | Common Stock-domestic [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	1,267	1,393
United States Pension Plans of US Entity, Defined Benefit [Member] | Other invested assets [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	564	600
United States Pension Plans of US Entity, Defined Benefit [Member] | Derivatives [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	8	44
United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at beginning of year	1,240	1,185
Purchases, Sales, Issuances and Settlements	0	0
Fair value of plan assets at end of year	1,320	1,240
United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member] | Corporate fixed maturity securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	169	143
United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member] | State and political subdivision securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	71	60
United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member] | Foreign government debt securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	51	13
United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member] | Other Debt Securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	58	89
United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member] | Common Stock-domestic [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	250	242
United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member] | Other invested assets [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	0	0
United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member] | Derivatives [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	1	1
Foreign Pension Plans, Defined Benefit [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at beginning of year	185	178
Purchases, Sales, Issuances and Settlements	(11)	(4)
Fair value of plan assets at end of year	224	185
Foreign Pension Plans, Defined Benefit [Member] | Foreign government debt securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	120	96
Foreign Pension Plans, Defined Benefit [Member] | Other invested assets [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	24	19
Foreign Pension Plans, Defined Benefit [Member] | Derivatives [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	13	13
Foreign Pension Plans, Defined Benefit [Member] | Real Estate [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	7	8
Level 3 [Member] | United States Pension Plans of US Entity, Defined Benefit [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	619	780
Level 3 [Member] | United States Pension Plans of US Entity, Defined Benefit [Member] | Corporate fixed maturity securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at beginning of year	32	49	68
Realized gains (losses)	0	0	0
Unrealized gains (losses)	(1)	(4)	7
Purchases, Sales, Issuances and Settlements	(12)	(13)	(17)
Transfers Into and/or Out of Level 3	0	0	(9)
Fair value of plan assets at end of year	19	32	49
Level 3 [Member] | United States Pension Plans of US Entity, Defined Benefit [Member] | State and political subdivision securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	0	0
Level 3 [Member] | United States Pension Plans of US Entity, Defined Benefit [Member] | Foreign government debt securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at beginning of year	5	4	5
Realized gains (losses)	0	0	0
Unrealized gains (losses)	8	(1)	1
Purchases, Sales, Issuances and Settlements	(5)	2	(2)
Transfers Into and/or Out of Level 3	0	0	0
Fair value of plan assets at end of year	8	5	4
Level 3 [Member] | United States Pension Plans of US Entity, Defined Benefit [Member] | Other Debt Securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at beginning of year	2	2	69
Realized gains (losses)	0	(1)	(11)
Unrealized gains (losses)	0	1	14
Purchases, Sales, Issuances and Settlements	5	(1)	(71)
Transfers Into and/or Out of Level 3	0	1	1
Fair value of plan assets at end of year	7	2	2
Level 3 [Member] | United States Pension Plans of US Entity, Defined Benefit [Member] | Common Stock-domestic [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at beginning of year	206	240	241
Realized gains (losses)	(27)	(59)	0
Unrealized gains (losses)	10	118	(2)
Purchases, Sales, Issuances and Settlements	(52)	(93)	1
Transfers Into and/or Out of Level 3	0	0	0
Fair value of plan assets at end of year	137	206	240
Level 3 [Member] | United States Pension Plans of US Entity, Defined Benefit [Member] | Other invested assets [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at beginning of year	531	471	373
Realized gains (losses)	55	85	78
Unrealized gains (losses)	(36)	45	(4)
Purchases, Sales, Issuances and Settlements	(103)	(70)	24
Transfers Into and/or Out of Level 3	0	0	0
Fair value of plan assets at end of year	447	531	471
Level 3 [Member] | United States Pension Plans of US Entity, Defined Benefit [Member] | Derivatives [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at beginning of year	4	0
Realized gains (losses)	6	2
Unrealized gains (losses)	(7)	4
Purchases, Sales, Issuances and Settlements	(2)	(2)
Transfers Into and/or Out of Level 3	0	0
Fair value of plan assets at end of year	1	4
Level 3 [Member] | United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	8	11
Level 3 [Member] | United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member] | Corporate fixed maturity securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at beginning of year	4	4	0
Realized gains (losses)	0	0	0
Unrealized gains (losses)	0	0	1
Purchases, Sales, Issuances and Settlements	0	0	0
Transfers Into and/or Out of Level 3	0	0	3
Fair value of plan assets at end of year	4	4	4
Level 3 [Member] | United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member] | State and political subdivision securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at beginning of year	1	1	0
Realized gains (losses)	0	0	0
Unrealized gains (losses)	0	0	0
Purchases, Sales, Issuances and Settlements	0	0	0
Transfers Into and/or Out of Level 3	0	0	1
Fair value of plan assets at end of year	1	1	1
Level 3 [Member] | United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member] | Foreign government debt securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	0	0
Level 3 [Member] | United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member] | Other Debt Securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at beginning of year	5	6	9
Realized gains (losses)	(2)	(1)	(4)
Unrealized gains (losses)	2	1	1
Purchases, Sales, Issuances and Settlements	(2)	(1)	(1)
Transfers Into and/or Out of Level 3	0	0	1
Fair value of plan assets at end of year	3	5	6
Level 3 [Member] | United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member] | Common Stock-domestic [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	0	0
Level 3 [Member] | United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member] | Other invested assets [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	0	0
Level 3 [Member] | United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member] | Derivatives [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at beginning of year	1	0
Realized gains (losses)	2	0
Unrealized gains (losses)	(2)	1
Purchases, Sales, Issuances and Settlements	(1)	0
Transfers Into and/or Out of Level 3	0	0
Fair value of plan assets at end of year	0	1
Level 3 [Member] | Foreign Pension Plans, Defined Benefit [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	20	21
Level 3 [Member] | Foreign Pension Plans, Defined Benefit [Member] | Foreign government debt securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	0	0
Level 3 [Member] | Foreign Pension Plans, Defined Benefit [Member] | Other invested assets [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at end of year	0	0
Level 3 [Member] | Foreign Pension Plans, Defined Benefit [Member] | Derivatives [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at beginning of year	13	11	0
Realized gains (losses)	(1)	0	3
Unrealized gains (losses)	1	2	(3)
Purchases, Sales, Issuances and Settlements	0	0	(1)
Transfers Into and/or Out of Level 3	0	0	12
Fair value of plan assets at end of year	13	13	11
Level 3 [Member] | Foreign Pension Plans, Defined Benefit [Member] | Real Estate [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3)
Fair value of plan assets at beginning of year	8	8	0
Realized gains (losses)	(1)	0	0
Unrealized gains (losses)	0	0	0
Purchases, Sales, Issuances and Settlements	0	0	0
Transfers Into and/or Out of Level 3	0	0	8
Fair value of plan assets at end of year	$ 7	$ 8	$ 8