Restructuring Costs (Restructuring Activities) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Restructuring Reserve [Roll Forward]
Liability at beginning of period	$ 181	$ 211
Amount Accrued	4	51
Cash Paid	(29)	(82)
Other	3	1
Liability at end of period	159	181
Severance [Member]
Restructuring Reserve [Roll Forward]
Liability at beginning of period	27	40
Amount Accrued	4	29
Cash Paid	(20)	(40)
Other	6	(2)
Liability at end of period	17	27
Future Rent Under Non-Cancelable Leases and Other Costs [Member]
Restructuring Reserve [Roll Forward]
Liability at beginning of period	154	171
Amount Accrued	0	22
Cash Paid	(9)	(42)
Other	(3)	3
Liability at end of period	$ 142	$ 154