Employee Benefit Plans (Significant Unobservable Inputs) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits U.S. Plans [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	$ 8,750	$ 7,305	$ 7,390
Pension Benefits U.S. Plans [Member] | Corporate fixed maturity securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	2,718	2,003
Pension Benefits U.S. Plans [Member] | Foreign government
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	735	685
Pension Benefits U.S. Plans [Member] | Municipals securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	270	206
Pension Benefits U.S. Plans [Member] | Other securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	196	479
Pension Benefits U.S. Plans [Member] | Common stock - domestic
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	951	1,224
Pension Benefits U.S. Plans [Member] | Other investments
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	767	563
Pension Benefits U.S. Plans [Member] | Derivative assets
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	90	63
Other Postretirement Benefits U.S. Plans [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	1,426	1,352	1,320
Other Postretirement Benefits U.S. Plans [Member] | Corporate fixed maturity securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	289	248
Other Postretirement Benefits U.S. Plans [Member] | Foreign government
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	68	63
Other Postretirement Benefits U.S. Plans [Member] | Municipals securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	74	70
Other Postretirement Benefits U.S. Plans [Member] | Other securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	63	54
Other Postretirement Benefits U.S. Plans [Member] | Common stock - domestic
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	188	196
Other Postretirement Benefits U.S. Plans [Member] | Other investments
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	0	0
Other Postretirement Benefits U.S. Plans [Member] | Derivative assets
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	1	3
Level 3 | Pension Benefits U.S. Plans [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	920	819
Level 3 | Pension Benefits U.S. Plans [Member] | Corporate fixed maturity securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at January 1,	55	18	30
Realized gains (losses)	3	0	0
Unrealized gains (losses)	0	(2)	(1)
Purchases, sales, issuances and settlements, net	11	17	(11)
Transfers into and/or out of Level 3	11	22	0
Fair value of plan assets at December 31,	80	55	18
Level 3 | Pension Benefits U.S. Plans [Member] | Foreign government
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at January 1,	10	7	5
Realized gains (losses)	0	0	0
Unrealized gains (losses)	0	1	8
Purchases, sales, issuances and settlements, net	5	(3)	(6)
Transfers into and/or out of Level 3	2	5	0
Fair value of plan assets at December 31,	17	10	7
Level 3 | Pension Benefits U.S. Plans [Member] | Municipals securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	0	0
Level 3 | Pension Benefits U.S. Plans [Member] | Other securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at January 1,	19	7	2
Realized gains (losses)	0	0	0
Unrealized gains (losses)	0	0	1
Purchases, sales, issuances and settlements, net	(2)	11	4
Transfers into and/or out of Level 3	(9)	1	0
Fair value of plan assets at December 31,	8	19	7
Level 3 | Pension Benefits U.S. Plans [Member] | Common stock - domestic
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at January 1,	139	129	194
Realized gains (losses)	0	(1)	(25)
Unrealized gains (losses)	0	9	9
Purchases, sales, issuances and settlements, net	0	2	(49)
Transfers into and/or out of Level 3	(139)	0	0
Fair value of plan assets at December 31,	0	139	129
Level 3 | Pension Benefits U.S. Plans [Member] | Other investments
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at January 1,	563	419	501
Realized gains (losses)	(13)	0	52
Unrealized gains (losses)	114	56	(38)
Purchases, sales, issuances and settlements, net	(104)	(58)	(96)
Transfers into and/or out of Level 3	183	146	0
Fair value of plan assets at December 31,	743	563	419
Level 3 | Pension Benefits U.S. Plans [Member] | Derivative assets
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at January 1,	33	1	4
Realized gains (losses)	(16)	(2)	4
Unrealized gains (losses)	19	(17)	(6)
Purchases, sales, issuances and settlements, net	34	51	(1)
Transfers into and/or out of Level 3	2	0	0
Fair value of plan assets at December 31,	72	33	1
Level 3 | Other Postretirement Benefits U.S. Plans [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	3	1
Level 3 | Other Postretirement Benefits U.S. Plans [Member] | Corporate fixed maturity securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at January 1,	1	4	4
Realized gains (losses)	0	0	0
Unrealized gains (losses)	1	0	0
Purchases, sales, issuances and settlements, net	1	(3)	0
Transfers into and/or out of Level 3	0	0	0
Fair value of plan assets at December 31,	3	1	4
Level 3 | Other Postretirement Benefits U.S. Plans [Member] | Foreign government
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	0	0
Level 3 | Other Postretirement Benefits U.S. Plans [Member] | Municipals securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at January 1,	0	1	1
Realized gains (losses)	0	0	0
Unrealized gains (losses)	0	0	0
Purchases, sales, issuances and settlements, net	0	(1)	0
Transfers into and/or out of Level 3	0	0	0
Fair value of plan assets at December 31,	0	0	1
Level 3 | Other Postretirement Benefits U.S. Plans [Member] | Other securities [Member]
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at January 1,	0	3	5
Realized gains (losses)	0	(3)	(2)
Unrealized gains (losses)	0	4	2
Purchases, sales, issuances and settlements, net	0	(4)	(2)
Transfers into and/or out of Level 3	0	0	0
Fair value of plan assets at December 31,	0	0	3
Level 3 | Other Postretirement Benefits U.S. Plans [Member] | Common stock - domestic
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	0	0
Level 3 | Other Postretirement Benefits U.S. Plans [Member] | Other investments
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at December 31,	0	0
Level 3 | Other Postretirement Benefits U.S. Plans [Member] | Derivative assets
Rollforward fair value measurement using significant unobservable inputs (level 3) [Roll Forward]
Fair value of plan assets at January 1,	0	0	1
Realized gains (losses)	0	0	2
Unrealized gains (losses)	0	0	(2)
Purchases, sales, issuances and settlements, net	0	0	(1)
Transfers into and/or out of Level 3	0	0	0
Fair value of plan assets at December 31,	$ 0	$ 0	$ 0