Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net Income	$ 3,577	$ 4,373	$ 4,526
Other comprehensive income (loss):
Net change in derivative contracts	(27)	(43)	(82)
Net change in pension and other benefits	(98)	(360)	163
Net change in investments	140	42	(45)
Total Other Comprehensive Income (Loss)	15	(361)	36
Comprehensive Income	$ 3,592	$ 4,012	$ 4,562