Equity-Based Compensation (Summary of Equity-Based Compensation) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity-based compensation	[1]	$ 12	$ 15	$ 33	$ 28
Intrinsic value of all settled equity-based awards		$ 8	$ 0	$ 110	$ 31

[1] Includes allocated expense for both executive directors and corporate executives of 21CF, allocated using a proportional allocation driver, which management has deemed to be reasonable.