Leases - Narrative (Details) - USD ($) $ in Millions		3 Months Ended
	Jan. 01, 2019	Mar. 31, 2019
Lessee, Lease, Description [Line Items]
Right-of-use asset recognized as non-cash asset addition	$ 534	$ 30
Cash paid for amounts included in measurement of operating lease liabilities		14
Operating lease costs		$ 18
Maximum
Lessee, Lease, Description [Line Items]
Term of lease agreements (up to)		50 years