Restructuring Charges (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended		30 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2013
Restructuring And Related Cost [Line Items]
Restructuring charges		$ 19	$ 43
Cumulative amount paid since restructuring activities began	15			42
Severance Costs [Member]
Restructuring And Related Cost [Line Items]
Restructuring charges		13	9
Cumulative amount paid since restructuring activities began				19
Contract Termination And Other Associated Costs [Member]
Restructuring And Related Cost [Line Items]
Restructuring charges		6	34
Cumulative amount paid since restructuring activities began				$ 23