Leases - Cash Flow From Lease Transactions (Details)	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Leases
Gains and losses on sale and leaseback transactions, net	$ 0	$ 41,000,000
Cash paid for amounts included in the measurement of lease liabilities
Operating cash outflows from finance leases		7,000,000
Financing cash outflows from finance leases		6,000,000
Operating cash outflows from operating leases		1,154,000,000
ROU assets obtained in exchange for new finance lease liabilities	149,000,000	149,000,000
ROU assets obtained in exchange for new operating lease liabilities	$ 6,023,000,000	6,023,000,000
ROU assets obtained in exchange for new finance lease liabilities - post adoption
ROU assets obtained in exchange for new operating lease liabilities - post adoption		$ 1,221,000,000