Employee Benefits - Schedule of changes in Level 3 fair value for U.S. Pension Plans (Details) - U.S. - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Actual return on plan assets:
Balance at the beginning of the period	$ 1,951	$ 2,036
Balance at the end of the period	1,683	1,951
Significant Unobservable Inputs (Level 3)
Actual return on plan assets:
Balance at the beginning of the period	0
Balance at the end of the period	$ 0	$ 0