Employee Benefits - Benefit Obligation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	$ 2,023
Fair value of plan assets at end of year	2,073	$ 2,023
Amounts recognized in consolidated balance sheets:
Non-current liabilities	(274)	(276)
Retirement Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Net benefit obligation at beginning of year	2,199	2,462
Service cost	3	6	$ 5
Interest cost	78	96	99
Plan participants’ contributions	0	0
Actuarial loss (gain)	196	(189)
Gross benefits paid	(121)	(150)
Foreign currency effect	(75)	(26)
Other adjustments	(20)	0
Net benefit obligation at end of year	2,260	2,199	2,462
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	2,023	2,236
Actual return on plan assets	259	(57)
Employer contributions	8	15
Plan participants’ contributions	0	0
Gross benefits paid	(121)	(150)
Foreign currency effect	(74)	(21)
Other adjustments	(22)	0
Fair value of plan assets at end of year	2,073	2,023	2,236
Funded status	(187)	(176)
Amounts recognized in consolidated balance sheets:
Non-current assets	46	36
Current liabilities	(8)	(8)
Non-current liabilities	(225)	(204)
Total amounts recognized in consolidated balance sheets	(187)	(176)
Accumulated benefit obligation	2,251	2,190
Plans with accumulated benefit obligation in excess of the fair value of plan assets:
Projected benefit obligation	674	1,810
Accumulated benefit obligation	665	1,801
Fair value of plan assets	441	1,598
Amounts recognized in accumulated other comprehensive loss, net of tax:
Net actuarial loss (gain)	483	433
Prior service credit	1	1
Total recognized	484	434
Postretirement Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Net benefit obligation at beginning of year	80	96
Service cost	0	0	1
Interest cost	2	3	4
Plan participants’ contributions	4	4
Actuarial loss (gain)	(6)	(12)
Gross benefits paid	(10)	(12)
Foreign currency effect	0	0
Other adjustments	(13)	1
Net benefit obligation at end of year	57	80	96
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	6	8
Plan participants’ contributions	4	4
Gross benefits paid	(10)	(12)
Foreign currency effect	0	0
Other adjustments	0	0
Fair value of plan assets at end of year	0	0	$ 0
Funded status	(57)	(80)
Amounts recognized in consolidated balance sheets:
Non-current assets	0	0
Current liabilities	(8)	(8)
Non-current liabilities	(49)	(72)
Total amounts recognized in consolidated balance sheets	(57)	(80)
Amounts recognized in accumulated other comprehensive loss, net of tax:
Net actuarial loss (gain)	(35)	(24)
Prior service credit	(13)	(5)
Total recognized	$ (48)	$ (29)