Employee Retirement Plans - Projected Benefit Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Change in Plan Assets:
Fair value as of beginning of period	$ 1,340
Fair value as of end of period	1,301	$ 1,340
Components on the Consolidated Balance Sheets:
Current liabilities	(18)	(22)
Noncurrent liabilities	(392)	(491)
Pension
Change in Benefit Obligation:
Benefit obligation as of beginning of period	1,686	1,376
Service cost	49	37	$ 38
Interest cost	66	65	63
Curtailment/settlements	(4)	(24)
Participant contributions	11	10
Benefits paid	(86)	(81)
Plan amendment	0	0
Actuarial (gain) loss	(119)	327
Foreign currency translation	(39)	(24)
Benefit obligation as of end of period	1,564	1,686	1,376
Change in Plan Assets:
Fair value as of beginning of period	1,340	1,262
Actual return on plan assets	17	132
Employer contributions	61	64
Participant contributions	11	10
Benefits paid	(86)	(81)
Curtailment/settlements	(4)	(24)
Foreign currency translation	(38)	(23)
Fair value as of end of period	1,301	1,340	1,262
Funded status	(263)	(346)
Components on the Consolidated Balance Sheets:
Noncurrent assets	3	0
Current liabilities	(9)	(9)
Noncurrent liabilities	(257)	(337)
Net liability as of December 31	(263)	(346)
Pretax Components in AOCI:
Net actuarial loss	387	490
Prior service credit	(1)	(1)
Total as of end of year	386	489
Postretirement
Change in Benefit Obligation:
Benefit obligation as of beginning of period	167	166
Service cost	2	3	3
Interest cost	6	7	7
Curtailment/settlements	0	0
Participant contributions	3	8
Benefits paid	(11)	(20)
Plan amendment	0	4
Actuarial (gain) loss	(14)	4
Foreign currency translation	(9)	(5)
Benefit obligation as of end of period	144	167	166
Change in Plan Assets:
Fair value as of beginning of period	0	0
Actual return on plan assets	0	0
Employer contributions	8	12
Participant contributions	3	8
Benefits paid	(11)	(20)
Curtailment/settlements	0	0
Foreign currency translation	0	0
Fair value as of end of period	0	0	$ 0
Funded status	(144)	(167)
Components on the Consolidated Balance Sheets:
Noncurrent assets	0	0
Current liabilities	(9)	(13)
Noncurrent liabilities	(135)	(154)
Net liability as of December 31	(144)	(167)
Pretax Components in AOCI:
Net actuarial loss	7	24
Prior service credit	(108)	(140)
Total as of end of year	$ (101)	$ (116)