Leases - Narrative (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 6	$ 12
Leases not yet commenced	$ 128	$ 128
Minimum
Lessee, Lease, Description [Line Items]
Operating lease, remaining lease terms		1 year
Leases not yet commenced, term	13 years	13 years
Maximum
Lessee, Lease, Description [Line Items]
Operating lease, remaining lease terms		8 years
Leases not yet commenced, term	20 years	20 years