Summary of Significant Accounting Policies - Operating Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Deferred contract costs		$ 8	$ 9
Document Period End Date	Dec. 31, 2019
Minimum
Lessee, Lease, Description [Line Items]
Operating lease initial term	5 years
Maximum
Lessee, Lease, Description [Line Items]
Operating lease initial term	10 years