Leases - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
ROU asset	$ 139	$ 139	$ 0
Operating lease liabilities	148	148	$ 0
Short-term lease cost (less than $1)	0	1
Finance lease liability	$ 4	$ 4
Minimum
Lessee, Lease, Description [Line Items]
Term of lease	1 year	1 year
Term of extension	3 years	3 years
Maximum
Lessee, Lease, Description [Line Items]
Term of lease	9 years	9 years
Term of extension	5 years	5 years