Leases - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Options to extend term	10 years
Assets recorded under finance leases	$ 48
Finance lease asset, accumulated depreciation	2
Operating lease not yet commenced	$ 39
Minimum
Lessee, Lease, Description [Line Items]
Lease renewal term	1 year
Options to terminate term	1 month
Operating leases not yet commenced lease term	2 years
Maximum
Lessee, Lease, Description [Line Items]
Lease renewal term	15 years
Options to terminate term	5 years
Operating leases not yet commenced lease term	15 years