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Equity And Earnings Per Share (Diluted Table) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Diluted earnings per share:
Net income available for common stockholders	$ 23	$ 27	$ 47	$ 60
Weighted Average Shares Outstanding [Abstract]
Weighted Average Number of Shares Outstanding, Basic	69,087,853	64,967,364	68,539,526	64,476,421
Potentially dilutive common shares:
Issuable pursuant to employee incentive plans	975,574	1,503,549	1,074,041	1,386,987
Weighted Average Number of Shares Outstanding, Diluted	70,063,427	66,470,913	69,613,567	65,863,408
Earnings Per Share, Diluted	$ 0.32	$ 0.40	$ 0.67	$ 0.91
Common Class A
Weighted Average Shares Outstanding [Abstract]
Weighted Average Number of Shares Outstanding, Basic	69,087,753	64,967,264	68,539,426	64,476,321
Common Class B
Weighted Average Shares Outstanding [Abstract]
Weighted Average Number of Shares Outstanding, Basic	100	100	100	100

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Potentially Dilutive Common Shares [Abstract]

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Net Income or Loss Available to Common Stockholders plus adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

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The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

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