Leases - Operating Lease Income and Related Depreciation Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Leases [Abstract]
Operating lease income	$ 1,384		$ 4,027
Operating lease income		$ 1,157		$ 3,316
Lessee, Lease, Description [Line Items]
Depreciation expense		$ 901		$ 2,564
Assets subject to operating leases
Lessee, Lease, Description [Line Items]
Depreciation expense	$ 1,053		$ 3,038