Employee Benefits Schedule of Changes in Fair Value of Plan Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 487	$ 473
Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	32	23	17
Purchases	7
Realized loss on sales	(2)
Purchases and sales, net		4
Realized gain on sales		1
Unrealized gain on assets	4	1
alternative assets [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	30	28	23
Purchases	0
Realized loss on sales	0
Purchases and sales, net		2
Realized gain on sales		0
Unrealized gain on assets	2	3
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	62	51	40
Purchases	7
Realized loss on sales	(2)
Purchases and sales, net		6
Realized gain on sales		1
Unrealized gain on assets	$ 6	$ 4