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Summary of Significant Accounting Policies - Contract Assets, Deferred Contract Costs and Deferred Revenue (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract assets	$ 22		$ 9
Deferred contract costs		$ 8	9
Aggregate current and long-term deferred revenue	$ 372		$ 401
Impact of ASU 2014-09 Increase (decrease) \| ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Aggregate current and long-term deferred revenue				$ 19