Condensed Consolidated Statements of Equity (Unaudited) - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Shares [Member]	Noncontrolling Interest [Member]
Balance at Dec. 31, 2013	$ 3,613	$ 595	$ 2,054	$ 1,063	$ (136)	$ (8)	$ 45
Balance (in shares) at Dec. 31, 2013		118,900,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	348			334			14
Other comprehensive income	3				3
Dividends on common stock	(175)			(175)
Distribution to noncontrolling interest	(17)						(17)
Stock granted, share-based compensation, net of forfeitures	(11)		(11)
Stock issued, dividend reinvestment plan	9	$ 1	8
Stock issued, dividend reinvestment plan (in shares)		100,000
Stock issued, share-based compensation, net of forfeitures	22	$ 3	19
Stock issued, share-based compensation, net of forfeitures (in shares)		600,000
Stock-based compensation expense, net of tax	10		10
Balance at Sep. 30, 2014	$ 3,802	$ 599	2,080	1,222	(133)	(8)	42
Balance, shares (in shares) at Sep. 30, 2014	119,564,666	119,600,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ (8)
Other comprehensive income	0
Balance at Sep. 30, 2014	$ 3,802	$ 599	2,080	1,222	(133)	(8)	42
Balance, shares (in shares) at Sep. 30, 2014	119,564,666	119,600,000
Balance at Dec. 31, 2014	$ 3,828	$ 599	2,087	1,312	(206)	(8)	44
Balance (in shares) at Dec. 31, 2014	119,647,149	119,600,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 261			246			15
Other comprehensive income	11				11		0
Dividends on common stock	(183)			(183)
Distribution to noncontrolling interest	(18)						(18)
Stock granted, share-based compensation, net of forfeitures	(13)		(13)
Stock issued, dividend reinvestment plan	9	$ 1	8
Stock issued, dividend reinvestment plan (in shares)		200,000
Stock issued, share-based compensation, net of forfeitures	14	$ 2	12
Stock issued, share-based compensation, net of forfeitures (in shares)		400,000
Stock-based compensation expense, net of tax	1		1
Balance at Sep. 30, 2015	$ 3,910	$ 602	2,095	1,375	(195)	(8)	41
Balance, shares (in shares) at Sep. 30, 2015	120,249,058	120,200,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 12
Other comprehensive income	(27)
Balance at Sep. 30, 2015	$ 3,910	$ 602	$ 2,095	$ 1,375	$ (195)	$ (8)	$ 41
Balance, shares (in shares) at Sep. 30, 2015	120,249,058	120,200,000