Accounting Pronouncements Future Minimum Payments Due on Operating Leases (Details) - USD ($) $ in Billions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Description	26
Adjustments for New Accounting Pronouncement [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Future minimum lease payments		$ 3.0