Retirement Benefits and Trusteed Assets Retirement Benefits and Trusteed Assets (Details 15) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plans Fair Value Measurements Using Significant Unobservale Inputs [Line Items]
Beginning Balance	$ 44	$ 59
Realized gains (losses)	60	87
Purchases	2	3
Ending Balance	(13)	44
The amount of total gains (losses) included in net income attributed to the change in unrealized gains or losses related to assets still held at the end of the period	58	75
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans Fair Value Measurements Using Significant Unobservale Inputs [Line Items]
Beginning Balance	155	134
Realized gains (losses)	(5)	1
Unrealized gains (losses)	14	(20)
Purchases	122	116
Sales	(81)	(76)
Ending Balance	205	155
The amount of total gains (losses) included in net income attributed to the change in unrealized gains or losses related to assets still held at the end of the period	8	(11)
Other Postretirement Benefit Plans, Defined Benefit [Member] | Hedge Funds and Similar Investments [Member]
Defined Benefit Plans Fair Value Measurements Using Significant Unobservale Inputs [Line Items]
Beginning Balance	95	79
Realized gains (losses)	6	(1)
Unrealized gains (losses)	0	2
Purchases	86	68
Sales	(68)	(53)
Ending Balance	119	95
The amount of total gains (losses) included in net income attributed to the change in unrealized gains or losses related to assets still held at the end of the period	6	5
Other Postretirement Benefit Plans, Defined Benefit [Member] | Private Equity and Other [Member]
Defined Benefit Plans Fair Value Measurements Using Significant Unobservale Inputs [Line Items]
Beginning Balance	60	55
Realized gains (losses)	(11)	2
Unrealized gains (losses)	14	(22)
Purchases	36	48
Sales	(13)	(23)
Ending Balance	86	60
The amount of total gains (losses) included in net income attributed to the change in unrealized gains or losses related to assets still held at the end of the period	2	(16)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans Fair Value Measurements Using Significant Unobservale Inputs [Line Items]
Beginning Balance	464	478
Realized gains (losses)	12	2
Unrealized gains (losses)	7	(29)
Purchases	283	87
Sales	(248)	(74)
Ending Balance	518	464
The amount of total gains (losses) included in net income attributed to the change in unrealized gains or losses related to assets still held at the end of the period	22	(24)
Pension Plans, Defined Benefit [Member] | Hedge Funds and Similar Investments [Member]
Defined Benefit Plans Fair Value Measurements Using Significant Unobservale Inputs [Line Items]
Beginning Balance	296	304
Realized gains (losses)	18	(4)
Unrealized gains (losses)	(5)	1
Purchases	250	64
Sales	(220)	(69)
Ending Balance	339	296
The amount of total gains (losses) included in net income attributed to the change in unrealized gains or losses related to assets still held at the end of the period	16	4
Pension Plans, Defined Benefit [Member] | Private Equity and Other [Member]
Defined Benefit Plans Fair Value Measurements Using Significant Unobservale Inputs [Line Items]
Beginning Balance	168	174
Realized gains (losses)	(6)	6
Unrealized gains (losses)	12	(30)
Purchases	33	23
Sales	(28)	(5)
Ending Balance	179	168
The amount of total gains (losses) included in net income attributed to the change in unrealized gains or losses related to assets still held at the end of the period	$ 6	$ (28)