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	$ 1	$ 2
Ending Balance	1	1
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	1	1
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans Fair Value Measurements Using Significant Unobservale Inputs [Line Items]
Beginning Balance	102	88
Realized gains (losses)	(3)	0
Unrealized gains (losses)	9	(12)
Purchases	81	76
Sales	(54)	(50)
Ending Balance	135	102
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	5	(8)
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	63	52
Realized gains (losses)	4	(1)
Unrealized gains (losses)	0	2
Purchases	56	45
Sales	(45)	(35)
Ending Balance	78	63
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	4	3
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	39	36
Realized gains (losses)	(7)	1
Unrealized gains (losses)	9	(14)
Purchases	25	31
Sales	(9)	(15)
Ending Balance	57	39
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	1	(11)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans Fair Value Measurements Using Significant Unobservale Inputs [Line Items]
Beginning Balance	321	324
Realized gains (losses)	9	1
Unrealized gains (losses)	5	(20)
Purchases	199	60
Sales	(171)	(44)
Ending Balance	363	321
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	15	(17)
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	205	206
Realized gains (losses)	13	(3)
Unrealized gains (losses)	(3)	1
Purchases	176	44
Sales	(153)	(43)
Ending Balance	238	205
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	11	3
Pension Plans, Defined Benefit [Member] | Private Equity and Other [Member]
Defined Benefit Plans Fair Value Measurements Using Significant Unobservale Inputs [Line Items]
Beginning Balance	116	118
Realized gains (losses)	(4)	4
Unrealized gains (losses)	8	(21)
Purchases	23	16
Sales	(18)	(1)
Ending Balance	125	116
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	$ 4	$ (20)