Leases - Other supplemental information (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)
Leases [Abstract]
Operating cash flows from operating leases		$ 161
Operating cash flows from finance leases	$ 13	28
Financing cash flows from finance leases		15
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability		1,138	[1]
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability		$ 65
Operating Lease, Weighted Average Remaining Lease Term	9 years 7 months 6 days	9 years 7 months 6 days
Finance Lease, Weighted Average Remaining Lease Term	6 years	6 years
Operating Lease, Weighted Average Discount Rate, Percent	4.60%	4.60%

[1] Primarily consists of operating lease right-of-use assets exchanged for lease obligations upon implementation of the new lease accounting standard on January 1, 2019.