Financial and Other Derivative Instruments (Details Textuals) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Letters of credit that could be used to offset net derivative liabilities	$ 2	$ 7
Letters of credit received that could be used to offset net derivative assets	2	2
Cash collateral posted, net of cash collateral received	79	37
Collateral adjustment on derivative assets	7	2
Collateral adjustment on derivative liabilities	84	36
Cash collateral paid	5	6
Cash collateral received	3	$ 3
Additional collateral, aggregate fair value	437
Derivative net liability position aggregate fair value	639
Collateral already posted fair value	2
Derivative net asset position, fair value	491
Remaining amount of offsets to derivative net liability positions for hard and soft trigger provisions	$ 146