Financial and Other Derivative Instruments (Details Textuals) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Letters of credit that could be used to offset net derivative liabilities	$ 1	$ 2
Letters of credit received that could be used to offset net derivative assets	3	2
Cash collateral posted, net of cash collateral received	44	34
Collateral adjustment on derivative assets	1	7
Collateral adjustment on derivative liabilities	24	28
Cash collateral paid	23	18
Cash collateral received	2	$ 5
Additional collateral, aggregate fair value	484
Derivative net liability position aggregate fair value	403
Collateral already posted fair value	2
Derivative net asset position, fair value	343
Remaining amount of offsets to derivative net liability positions for hard and soft trigger provisions	$ 58