Leases (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Lessor, operating lease, renewal term	10 years
Lessor, operating lease, option to terminate	1 year
Operating lease costs	$ 38
Operating lease, lease not yet commenced, assumption and judgment, value of underlying asset, amount	$ 210
Minimum
Lessee, Lease, Description [Line Items]
Lessee, operating lease, term of contract	1 year
Lessee, operating lease, lease not yet commenced, term of contract	3 years
Maximum
Lessee, Lease, Description [Line Items]
Lessee, operating lease, term of contract	19 years
Lessee, operating lease, lease not yet commenced, term of contract	11 years