Summary of Significant Accounting Policies (Amounts Attributable to Controlling Interests) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Net Income Attributable to Noncontrolling Interest	$ (22)	$ 5	$ 18
Income (Loss) from Continuing Operations Attributable to Noncontrolling Interests	$ (22)	$ 5	7
Income (Loss) from Discontinued Operations Attributable to Noncontrolling Interest, net of tax			$ 11

Amount after tax of income (loss) from a discontinued operation attributable to the noncontrolling interest. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

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