Employee Benefits - Schedule of changes in Level 3 fair value for U.S. Pension Plans (Details) - U.S. [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Change in fair value of plan assets
Balance at the beginning of the period	$ 2,036	$ 1,855
Actual return on plan assets:
Balance at the end of the period	1,951	2,036
Significant Unobservable Inputs (Level 3)
Change in fair value of plan assets
Balance at the beginning of the period	624	266
Actual return on plan assets:
Relating to assets still held at the end of the year	(4)	32
Relating to assets sold during the year	(3)	5
Purchases, sales and settlements—net	24	321
Transfer in/(out) of Level 3	0	0
Balance at the end of the period	$ 641	$ 624