Employee Benefit Plans (Pension plan and other postretirement plan assets that are measured at fair value and included in the Level 3 fair value category) (Details) (Fair Value, Inputs, Level 3 [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Pension Benefits [Member]
Fair value of plan assets at beginning of year	$ 1,278	$ 1,317	$ 1,220
Actual Return on Plan Assets
Relating to assets still held at the reporting date	128	118	56
Relating to assets sold during the period	(67)		0
Purchases	215	182	170
Sales	(269)	(339)	(129)
Fair value of plan assets at end of year	1,285	1,278	1,317
Pension Benefits [Member] | Private Equity [Member]
Fair value of plan assets at beginning of year	400	344	267
Actual Return on Plan Assets
Relating to assets still held at the reporting date	70	56	128
Relating to assets sold during the period	(34)		1
Purchases	76	90	53
Sales	(64)	(90)	(105)
Fair value of plan assets at end of year	448	400	344
Pension Benefits [Member] | Debt [Member]
Fair value of plan assets at beginning of year	262	241	191
Actual Return on Plan Assets
Relating to assets still held at the reporting date	10	27	19
Relating to assets sold during the period	(10)		0
Purchases	34	36	35
Sales	(53)	(42)	(4)
Fair value of plan assets at end of year	243	262	241
Pension Benefits [Member] | Hedge Funds [Member]
Fair value of plan assets at beginning of year	345	388	324
Actual Return on Plan Assets
Relating to assets still held at the reporting date	10	27	0
Relating to assets sold during the period	(15)		0
Purchases	48	0	64
Sales	(98)	(70)	0
Fair value of plan assets at end of year	290	345	388
Pension Benefits [Member] | Real Estate [Member]
Fair value of plan assets at beginning of year	271	344	438
Actual Return on Plan Assets
Relating to assets still held at the reporting date	38	8	(91)
Relating to assets sold during the period	(8)		(1)
Purchases	57	56	18
Sales	(54)	(137)	(20)
Fair value of plan assets at end of year	304	271	344
Other Postretirement Benefits [Member]
Fair value of plan assets at beginning of year	140	135	122
Actual Return on Plan Assets
Relating to assets still held at the reporting date	15	12	7
Relating to assets sold during the period	(6)		0
Purchases	16	20	21
Sales	(28)	(27)	(15)
Fair value of plan assets at end of year	137	140	135
Other Postretirement Benefits [Member] | Private Equity [Member]
Fair value of plan assets at beginning of year	61	54	47
Actual Return on Plan Assets
Relating to assets still held at the reporting date	11	9	13
Relating to assets sold during the period	(4)		0
Purchases	8	9	6
Sales	(13)	(11)	(12)
Fair value of plan assets at end of year	63	61	54
Other Postretirement Benefits [Member] | Debt [Member]
Fair value of plan assets at beginning of year	40	36	28
Actual Return on Plan Assets
Relating to assets still held at the reporting date	1	2	3
Relating to assets sold during the period	(1)		0
Purchases	3	8	7
Sales	(7)	(6)	(2)
Fair value of plan assets at end of year	36	40	36
Other Postretirement Benefits [Member] | Hedge Funds [Member]
Fair value of plan assets at beginning of year	17	19	15
Actual Return on Plan Assets
Relating to assets still held at the reporting date	0	1	0
Relating to assets sold during the period	(1)		0
Purchases	2	0	4
Sales	(4)	(3)	0
Fair value of plan assets at end of year	14	17	19
Other Postretirement Benefits [Member] | Real Estate [Member]
Fair value of plan assets at beginning of year	22	26	32
Actual Return on Plan Assets
Relating to assets still held at the reporting date	3	0	(9)
Relating to assets sold during the period	0		0
Purchases	3	3	4
Sales	(4)	(7)	(1)
Fair value of plan assets at end of year	$ 24	$ 22	$ 26