Restructuring (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Restructuring Reserve.
Balance at beginning of the period	$ 7	$ 0
Costs charged to expense		25
Costs paid or otherwise settled	(4)	(18)
Balance at end of the period	3	7
Severance
Restructuring Reserve.
Balance at beginning of the period	4	0
Costs charged to expense		20
Costs paid or otherwise settled	(4)	(16)
Balance at end of the period	0	4
Facilities costs
Restructuring Reserve.
Balance at beginning of the period	3	0
Costs charged to expense		4
Costs paid or otherwise settled	0	(1)
Balance at end of the period	3	3
Contract Termination Costs
Restructuring Reserve.
Balance at beginning of the period	0	0
Costs charged to expense		1
Costs paid or otherwise settled	0	(1)
Balance at end of the period	$ 0	$ 0