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Equity And Earnings Per Share (Diluted Table) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Diluted earnings per share:
Net income available for common stockholders	$ 39	$ 31	$ 126	$ 78
Weighted Average Shares Outstanding [Abstract]
Weighted Average Number of Shares Outstanding, Basic	74,649,469	71,109,577	72,879,007	69,405,624
Potentially dilutive common shares:
Issuable pursuant to employee incentive plans	710,620	863,906	866,633	1,003,995
Weighted Average Number of Shares Outstanding, Diluted	75,360,089	71,973,483	73,745,640	70,409,619
Earnings Per Share, Diluted	$ 0.51	$ 0.43	$ 1.71	$ 1.10
Common Class A
Weighted Average Shares Outstanding [Abstract]
Weighted Average Number of Shares Outstanding, Basic	74,649,369	71,109,477	72,878,907	69,405,524
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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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities, and addition from assumption of issuance of common shares for dilutive potential common shares; of income (loss) available to common shareholders.

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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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