Description of Business and Basis of Presentation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	Sep. 30, 2019	Jul. 01, 2019	Jun. 30, 2019	Mar. 19, 2019
Disclosure Basis Of Presentation Details [Line Items]
Operating lease liabilities	$ 605
ROU assets	$ 560		$ 0
Accounting Standards Update 2016-02
Disclosure Basis Of Presentation Details [Line Items]
Operating lease liabilities		$ 635
ROU assets		$ 585
Class A Common Stock
Disclosure Basis Of Presentation Details [Line Items]
Common stock, shares outstanding	354,475,255		354,422,419	354,000,000
Common stock, par value	$ 0.01		$ 0.01	$ 0.01
Class B Common Stock
Disclosure Basis Of Presentation Details [Line Items]
Common stock, shares outstanding	266,173,651		266,173,651	266,000,000
Common stock, par value	$ 0.01		$ 0.01	$ 0.01