Leases - Narrative (Details) - USD ($)	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 104,000,000
Operating lease commitments, not yet commenced	82,000,000
Financing lease commitments	0
Operating lease commitments	993,000,000
Lease liabilities, noncurrent	$ 660,000,000	$ 0
Weighted average remaining lease term for operating lease	7 years
Weighted average operating discount rate used to determine the operating lease	5.00%
Operating cash flow payments	$ 100,000,000
Operating lease, right-of-use asset	$ 61,000,000
Maximum
Lessee, Lease, Description [Line Items]
Operating lease commitments term, not yet commenced	15 years