Leases - Narrative (Details) - USD ($) $ in Millions		3 Months Ended	6 Months Ended
	Jan. 01, 2019	Jun. 30, 2019	Jun. 30, 2019
Lessee, Lease, Description [Line Items]
Right-of-use asset recognized as non-cash asset addition	$ 534		$ 40
Cash paid for amounts included in measurement of operating lease liabilities			28
Operating lease costs		$ 21	$ 39
Maximum
Lessee, Lease, Description [Line Items]
Term of lease agreements (up to)		50 years	50 years