Derivatives and Hedging Activities (Details Textuals) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivatives And Hedging Activities Textuals [Abstract]
Net reduction in interest expense on long term debt	$ 53	$ 126	$ 177
Derivative [Line Items]
Ineffectiveness reclassified from AOCI into income	0	0	0
Margin on interest rate swap not netted	115	144
Fair Value Hedging [Member]
Derivative [Line Items]
Notional amount of long-term debt	16,200	14,800
Net Investment Hedging [Member]
Derivative [Line Items]
Effective portion of gain (loss) on hedges	(174)	80	235
Other expense [Member]
Derivative [Line Items]
Gain in Changes of Fair Value of Derivatives not designated as hedges	$ 21	$ 1	$ 14