Derivative Financial Instruments and Risk Management (Details 5) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Offsetting Assets and Liabilities
Gross Amount of Recognized Assets	$ 22	$ 72
Gross Amounts Offset	0	0
Net Amount of Assets	22	72
Gross Amounts Not Offset	(10)	(7)
Net Amount	12	65
Gross Amount of Recognized Liabilities	(68)	(8)
Gross Amounts Offset	0	0
Net Amount of Liabilities	(68)	(8)
Gross Amounts Not Offset	10	7
Net Amount	$ (58)	$ (1)