Background and Basis of Presentation Level 4 (Details) - Accounting Changes and Error Corrections (USD $) In Millions, unless otherwise specified	6 Months Ended				3 Months Ended	6 Months Ended			6 Months Ended	12 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2012 Accelerated depreciation [Member]	Jun. 30, 2012 Accelerated depreciation [Member]	Jun. 30, 2012 As Previously Reported [Member]	Dec. 31, 2011 As Previously Reported [Member]	Jun. 30, 2012 Cash and Cash Equivalents [Member]	Dec. 31, 2011 Cash and Cash Equivalents [Member]	Jun. 30, 2012 Net cash provided by operating activities [Member]
Net Cash Provided by (Used in) Operating Activities	$ (65)	$ (10)					$ (11)
Prior Period Reclassification Adjustment					1	7			(11)	(12)	1
Cash and Cash Equivalents, at Carrying Value	$ 335	$ 322	$ 419	$ 416			$ 333	$ 428