Leases (Supplemental Cash Flow Information) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Leases [Abstract]
Operating cash flows from operating leases	$ 3,550
Operating cash flows from finance leases	65
Financing cash flows from finance leases	366
Right-of-use assets obtained in exchange for new operating lease liabilities	3,591
Right-of-use assets obtained in exchange for new finance lease liabilities	$ 0