Financial and Derivative Instruments Financial and Derivative Instruments (Details 2) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Offsetting Assets [Abstract]
Derivative Asset, Gross Amount Recognized	$ 2,459	$ 4,004
Derivative Asset, Gross Amounts Offset	2,254	3,591
Derivative Asset, Net Amounts Presented	205	413
Derivative Assets, Gross Amounts Not Offset	0	7
Derivative Asset, Net Amount	205	406
Offsetting Liabilities [Abstract]
Derivative Liability, Gross Amount Recognized	2,307	3,675
Derivative Liability, Gross Amounts Offset	2,254	3,591
Derivative Liability, Net Amounts Presented	53	84
Derivative Liabilities, Gross Amounts Not Offset	0	0
Derivative Liability, Net Amount	$ 53	$ 84