Contingencies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Guarantor Obligations [Line Items]
Guarantor Exposure as percent of outstanding loans	20.00%
Property Lease Guarantee [Member]
Guarantor Obligations [Line Items]
Year longest lease expires	2065
Potential amount of undiscounted payments we could be required to make in the event of non-payment	$ 525
Present value of potential payments we could be required to make in the event of non-payment	$ 425