Leases - Supplemental Cash Flow Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Leases [Abstract]
Operating cash flows from operating leases	$ 387
Operating cash flows from finance leases	11
Financing cash flows from finance leases	5
Operating lease right-of-use assets obtained in exchange for new operating lease liabilities	206
Right-of-use assets obtained in exchange for new finance lease liabilities	$ 12