Related Party Transactions and 21CF Investment (Components of Net (Decrease) Increase in 21CF Investment) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Net (decrease) increase in 21CF investment		$ (642)	$ 472	$ 23	$ 458
21CF Investment
Related Party Transaction [Line Items]
Cash pooling and general financing activities	[1]	(594)	389	(14)	321
Corporate allocations		95	83	180	137
Net (decrease) increase in 21CF investment		$ (499)	$ 472	$ 166	$ 458

[1] The nature of activities included in the line item ‘Cash pooling and general financing activities’ includes financing activities, capital transfers, cash sweeps, other treasury services and Direct Corporate Expenses. As part of this activity and prior to December 31, 2017, the majority of the cash balances are swept to 21CF on a daily basis and the Company receives capital from 21CF for the Company’s cash needs. Effective January 1, 2018, the Company ceased participating in 21CF’s capital and cash management accounts.