Other Intangible Assets (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	30 years
Amortization of Intangible Assets		$ 333	$ 347	$ 356
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months		312
Finite-Lived Intangible Assets, Amortization Expense, Year Two		312
Finite-Lived Intangible Assets, Amortization Expense, Year Three		312
Finite-Lived Intangible Assets, Amortization Expense, Year Four		312
Finite-Lived Intangible Assets, Amortization Expense, Year Five		312
Contractual customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross		9,232	10,027
Finite-Lived Intangible Assets, Accumulated Amortization		$ (1,465)	$ (1,283)