Retirement Plans (Details 11) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
U.S. Equity [Member]
Reconciliation of Level 3 assets held during the year
Beginning Balance	$ 73	$ 31
Net Realized Unrealized Gains/(Losses)	5	11
Net Purchases and Settlements	(12)	7
Net Transfers Into/(Out of) Level 3	0	24
Ending Balance	66	73
Absolute Return Hedge Funds [Member]
Reconciliation of Level 3 assets held during the year
Beginning Balance	87	81
Net Realized Unrealized Gains/(Losses)	1	11
Net Purchases and Settlements	(8)	(5)
Net Transfers Into/(Out of) Level 3	0
Ending Balance	80	87
Equity Hedge Funds [Member]
Reconciliation of Level 3 assets held during the year
Beginning Balance	63	58
Net Realized Unrealized Gains/(Losses)	(4)	2
Net Purchases and Settlements	(9)	3
Net Transfers Into/(Out of) Level 3	0
Ending Balance	50	63
Private Equity [Member]
Reconciliation of Level 3 assets held during the year
Beginning Balance	41	62
Net Realized Unrealized Gains/(Losses)	6	4
Net Purchases and Settlements	0	(1)
Net Transfers Into/(Out of) Level 3	0	(24)
Ending Balance	47	41
Private Real Assets [Member]
Reconciliation of Level 3 assets held during the year
Beginning Balance	10	7
Net Realized Unrealized Gains/(Losses)	1	1
Net Purchases and Settlements	5	2
Net Transfers Into/(Out of) Level 3	0
Ending Balance	16	10
Public Real Assets [Member]
Reconciliation of Level 3 assets held during the year
Beginning Balance	12	0
Net Realized Unrealized Gains/(Losses)	(3)	2
Net Purchases and Settlements	0	10
Net Transfers Into/(Out of) Level 3	0
Ending Balance	$ 9	$ 12