Pension and Other Postretirement Employee Benefit Plans - Changes In Level 3 Fair Value Measurements (Details 10) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined benefit pension plan, U.S. [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, end of year	$ 14,354	$ 13,012	$ 10,472
Defined benefit pension plan, U.S. [Member] | Equities [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, end of year	5,449
Defined benefit pension plan, U.S. [Member] | Common/collective trust funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Transfers in and/or out of level 3		0
Fair value of plan assets, end of year	1,312	2,271
Defined benefit pension plan, U.S. [Member] | Total limited partnerships [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, end of year	3,871	4,565
Defined benefit pension plan, U.S. [Member] | Hedge funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Transfers in and/or out of level 3		0
Fair value of plan assets, end of year	1,073	2,044
Defined benefit pension plan, U.S. [Member] | Private equity investments [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, end of year	1,969	1,743
Defined benefit pension plan, U.S. [Member] | Real estate [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, end of year	558	467
Defined benefit pension plan, U.S. [Member] | Real assets [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, end of year	271	311
Defined benefit pension plan, U.S. [Member] | Corporate debt securities [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, end of year	1,230	1,115
Defined benefit pension plan, U.S. [Member] | Other plan asset category [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, end of year	1,685	461
OPEB Plans [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, end of year	1,757	1,563	1,435
Level 3 [Member] | Defined benefit pension plan, U.S. [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, beginning of year	4,311	3,608	3,278
Realized gains/(losses)	329	78	88
Unrealized gains/(losses)	218	150	104
Purchases, sales and settlements, net	(891)	471	137
Transfers in and/or out of level 3	(6)	4	1
Fair value of plan assets, end of year	3,961	4,311	3,608
Level 3 [Member] | Defined benefit pension plan, U.S. [Member] | Equities [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, beginning of year	4	1	0
Realized gains/(losses)	0	0	0
Unrealized gains/(losses)	0	(1)	0
Purchases, sales and settlements, net	0	0	0
Transfers in and/or out of level 3	0	4	1
Fair value of plan assets, end of year	4	4	1
Level 3 [Member] | Defined benefit pension plan, U.S. [Member] | Common/collective trust funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, beginning of year	199	202	194
Realized gains/(losses)	59	2	35
Unrealized gains/(losses)	(32)	22	1
Purchases, sales and settlements, net	(222)	(27)	(28)
Transfers in and/or out of level 3	0		0
Fair value of plan assets, end of year	4	199	202
Level 3 [Member] | Defined benefit pension plan, U.S. [Member] | Total limited partnerships [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, beginning of year	3,687	2,976	2,696
Realized gains/(losses)	270	76	53
Unrealized gains/(losses)	240	136	62
Purchases, sales and settlements, net	(669)	499	165
Transfers in and/or out of level 3	(12)	0	0
Fair value of plan assets, end of year	3,516	3,687	2,976
Level 3 [Member] | Defined benefit pension plan, U.S. [Member] | Hedge funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, beginning of year	1,166	1,039	1,160
Realized gains/(losses)	137	1	(16)
Unrealized gains/(losses)	14	71	27
Purchases, sales and settlements, net	(593)	55	(76)
Transfers in and/or out of level 3	(6)		(56)
Fair value of plan assets, end of year	718	1,166	1,039
Level 3 [Member] | Defined benefit pension plan, U.S. [Member] | Private equity investments [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, beginning of year	1,743	1,367	1,232
Realized gains/(losses)	108	59	56
Unrealized gains/(losses)	170	54	2
Purchases, sales and settlements, net	(4)	263	77
Transfers in and/or out of level 3	(48)	0	0
Fair value of plan assets, end of year	1,969	1,743	1,367
Level 3 [Member] | Defined benefit pension plan, U.S. [Member] | Real estate [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, beginning of year	467	306	304
Realized gains/(losses)	21	16	8
Unrealized gains/(losses)	44	1	40
Purchases, sales and settlements, net	26	144	14
Transfers in and/or out of level 3	0	0	(60)
Fair value of plan assets, end of year	558	467	306
Level 3 [Member] | Defined benefit pension plan, U.S. [Member] | Real assets [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, beginning of year	311	264	0
Realized gains/(losses)	4	0	5
Unrealized gains/(losses)	12	10	(7)
Purchases, sales and settlements, net	(98)	37	150
Transfers in and/or out of level 3	42	0	116
Fair value of plan assets, end of year	271	311	264
Level 3 [Member] | Defined benefit pension plan, U.S. [Member] | Corporate debt securities [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, beginning of year	1	2	1
Realized gains/(losses)	0	0	0
Unrealized gains/(losses)	0	0	0
Purchases, sales and settlements, net	0	(1)	1
Transfers in and/or out of level 3	6	0	0
Fair value of plan assets, end of year	7	1	2
Level 3 [Member] | Defined benefit pension plan, U.S. [Member] | Other plan asset category [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, beginning of year	420	427	387
Realized gains/(losses)	0	0	0
Unrealized gains/(losses)	10	(7)	41
Purchases, sales and settlements, net	0	0	(1)
Transfers in and/or out of level 3	0	0	0
Fair value of plan assets, end of year	430	420	427
Level 3 [Member] | OPEB Plans [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, beginning of year	1,554	1,427	1,381
Realized gains/(losses)	0	0	0
Unrealized gains/(losses)	195	127	70
Purchases, sales and settlements, net	0	0	(24)
Transfers in and/or out of level 3	0	0	0
Fair value of plan assets, end of year	1,749	1,554	1,427
Level 3 [Member] | OPEB Plans [Member] | COLI [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets:
Fair value of plan assets, beginning of year	1,554	1,427	1,381
Realized gains/(losses)	0	0	0
Unrealized gains/(losses)	195	127	70
Purchases, sales and settlements, net	0	0	(24)
Transfers in and/or out of level 3	0	0	0
Fair value of plan assets, end of year	$ 1,749	$ 1,554	$ 1,427