Retirement Benefits - Fair Value Unobservable (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Actual return on plan assets:
Transfers into (out of) Level 3	$ (188.00)
Pension Plans Defined Benefit [Member]
Defined Benefit Plan Fair Value Of Plan Assets Unobservable Input Reconciliation [Line Items]
Fair value of net plan assets at beginning of year	2,426.00	1,044.00
Actual return on plan assets:
Relating to assets still held at the reporting date	217.00	104.00
Purchases	689.00	1,356.00
Sales	(6.00)	0
Settlements	(160.00)	(78.00)
Transfers into (out of) Level 3	(751.00)
Fair value of net plan assets at end of year	2,415.00	2,426.00
Other Postretirement Benefit Plans Defined Benefit [Member]
Defined Benefit Plan Fair Value Of Plan Assets Unobservable Input Reconciliation [Line Items]
Fair value of net plan assets at beginning of year	165.00	13.00
Actual return on plan assets:
Relating to assets still held at the reporting date	14.00	(4.00)
Purchases	123.00	156.00
Settlements	(1.00)
Transfers into (out of) Level 3	(193.00)
Fair value of net plan assets at end of year	108.00	165.00
Hedge Fund Investments [Member] | Pension Plans Defined Benefit [Member]
Defined Benefit Plan Fair Value Of Plan Assets Unobservable Input Reconciliation [Line Items]
Fair value of net plan assets at beginning of year	1,525.00
Actual return on plan assets:
Relating to assets still held at the reporting date	138.00	(26.00)
Purchases	447.00	1,222.00
Sales	(6.00)
Settlements	(4.00)
Transfers into (out of) Level 3	(865.00)
Fair value of net plan assets at end of year	1,235.00	1,525.00
Hedge Fund Investments [Member] | Other Postretirement Benefit Plans Defined Benefit [Member]
Defined Benefit Plan Fair Value Of Plan Assets Unobservable Input Reconciliation [Line Items]
Fair value of net plan assets at beginning of year	157.00	5.00
Actual return on plan assets:
Relating to assets still held at the reporting date	11.00	(3.00)
Purchases	32.00	155.00
Fair value of net plan assets at end of year	12.00	157.00
Commingled Funds In Private Equity Investments [Member] | Pension Plans Defined Benefit [Member]
Defined Benefit Plan Fair Value Of Plan Assets Unobservable Input Reconciliation [Line Items]
Fair value of net plan assets at beginning of year	672.00	536.00
Actual return on plan assets:
Relating to assets still held at the reporting date	55.00	84.00
Purchases	108.00	121.00
Sales	0
Settlements	(128.00)	(69.00)
Transfers into (out of) Level 3	47.00
Fair value of net plan assets at end of year	754.00	672.00
Commingled Funds In Private Equity Investments [Member] | Other Postretirement Benefit Plans Defined Benefit [Member]
Defined Benefit Plan Fair Value Of Plan Assets Unobservable Input Reconciliation [Line Items]
Fair value of net plan assets at beginning of year	1.00
Actual return on plan assets:
Purchases	0	1.00
Fair value of net plan assets at end of year	1.00	1.00
Commingled Funds In Direct Real Estate [Member] | Pension Plans Defined Benefit [Member]
Defined Benefit Plan Fair Value Of Plan Assets Unobservable Input Reconciliation [Line Items]
Fair value of net plan assets at beginning of year	229.00	179.00
Actual return on plan assets:
Relating to assets still held at the reporting date	24.00	46.00
Purchases	134.00	13.00
Sales	0	0
Settlements	(28.00)	(9.00)
Transfers into (out of) Level 3	67.00
Fair value of net plan assets at end of year	426.00	229.00
Commingled Funds In Direct Real Estate [Member] | Other Postretirement Benefit Plans Defined Benefit [Member]
Defined Benefit Plan Fair Value Of Plan Assets Unobservable Input Reconciliation [Line Items]
Fair value of net plan assets at beginning of year	7.00	8.00
Actual return on plan assets:
Relating to assets still held at the reporting date	3.00	(1.00)
Purchases		0
Settlements	(1.00)
Transfers into (out of) Level 3	(5.00)	0
Fair value of net plan assets at end of year	$ 95.00	$ 7.00