Schedule of Equity (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Jun. 30, 2013	Sep. 30, 2013	Sep. 30, 2012
Common Stock, Shares, Outstanding beginning of period			75,556,272	75,556,272
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			$ 1,730	$ 1,730
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs				3
Proceeds from Issuance of Common Stock	20		47	67	0
Net Income (Loss) Attributable to Parent	31	38		58	113
Net Income (Loss) Attributable to Noncontrolling Interest	0	(1)		(1)	(1)
Common Stock, Shares, Outstanding end of period	78,067,299			78,067,299
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,793			1,793
Common Stock [Member]
Common Stock, Shares, Outstanding beginning of period			75,556,272	75,556,272	75,362,956
Stock Issued During Period, Shares, New Issues	700,000		1,665,000	2,365,000
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures				146,027	171,430
Common Stock, Shares, Outstanding end of period	78,067,299	75,534,386		78,067,299	75,534,386
Common Stock Including Additional Paid in Capital [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			841	841	836
Proceeds from Issuance of Common Stock				67
Share-based Compensation				2	2
Dividends, Common Stock				0	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	910	838		910	838
Accumulated Other Comprehensive Income (Loss) [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			(6)	(6)	(6)
Share-based Compensation				0	0
Dividends, Common Stock				0	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(6)	(6)		(6)	(6)
Retained Earnings [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			893	893	833
Share-based Compensation				0	0
Dividends, Common Stock				(63)	(61)
Net Income (Loss) Attributable to Parent					113
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	888	885		888	885
Noncontrolling Interest [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			2	2	3
Share-based Compensation				0	0
Dividends, Common Stock				0	0
Net Income (Loss) Attributable to Noncontrolling Interest					(1)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 1	$ 2		$ 1	$ 2