Leases - Other supplemental information (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Leases [Abstract]
Operating cash flows from operating leases		$ 236
Operating cash flows from finance leases	$ 12	40
Financing cash flows from finance leases		19
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability		1,220	[1]
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability		$ 69
Operating Lease, Weighted Average Remaining Lease Term	9 years 4 months 24 days	9 years 4 months 24 days
Finance Lease, Weighted Average Remaining Lease Term	5 years 8 months 12 days	5 years 8 months 12 days
Operating Lease, Weighted Average Discount Rate, Percent	4.50%	4.50%

[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.