Employee Benefit Plans - Defined Contribution Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Contribution Plan, Cost Recognized	$ 102	$ 90	$ 83
Domestic Other Postretirement Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost Not Yet Recognized, Regulatory Deferrals, Before Tax	$ (7)	$ (8)