Accounting Pronouncements Future Minimum Payments Due on Operating Leases (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Lease Income, Lease Payments	$ 2,300
Future minimum lease payments	$ 2,721	[1]

[1] Excludes leases having non-cancelable lease terms of less than one year and per diem leases.