Pension, Other Postretirement Benefits and Savings Plans - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Curtailments/settlements			$ (137)	$ (33)
Defined contribution plans, contribution expenses			125	112	$ 106
U.S. Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, Lump Sum Program, payments			190
Total benefits cost			190	107	175
Curtailments/settlements			(137)	(32)	$ 0
Pension contributions	$ 1,167
Estimated net actuarial loss that will be amortized from AOCL into benefits cost in 2016			(108)
Postretirement benefits funded status			$ (327)	$ (257)
Weighted average discount rate			3.89%	4.40%	3.77%
Assumed weighted average long term rate of return			5.00%	5.47%	7.16%
Company contributions to plan assets			$ 0	$ 1,167
U.S. Pension Plans | Debt securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			94.00%
U.S. Pension Plans | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			6.00%
Other Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Pension contributions	907
Curtailment gains (charges)	(33)
United States Postretirement Benefit Plan of US Entity
Defined Benefit Plan Disclosure [Line Items]
Total benefits cost			$ (28)	(24)	$ (24)
Postretirement benefits funded status			$ (164)	$ (190)
Weighted average discount rate			3.59%	4.06%	3.30%
Foreign Postretirement Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Total benefits cost			$ 8	$ 9	$ 15
Postretirement benefits funded status			$ (124)	$ (166)
Weighted average discount rate			4.89%	6.62%	5.64%
Non-U.S. Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Total benefits cost			$ 84	$ 70	$ 114
Curtailments/settlements			(2)	13	$ (4)
Estimated net actuarial loss that will be amortized from AOCL into benefits cost in 2016			(27)
Postretirement benefits funded status			$ (315)	$ (457)
Weighted average discount rate			3.31%	4.36%	4.12%
Assumed weighted average long term rate of return			4.12%	5.12%	5.01%
Unfunded pension plans, accumulated pension benefit obligation			$ 233	$ 288
Unfunded pension plans, pension benefit obligation			256	348
Unfunded pension plans, AOCL adjustment			68	132
Company contributions to plan assets			$ 60	118
Non-U.S. Pension Plans | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			10.00%
Non-U.S. Pension Plans | Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			80.00%
Non-U.S. Pension Plans | Alternatives
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			10.00%
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total benefits cost			$ (20)	(15)	$ (9)
Curtailments/settlements			0	0	$ 0
Estimated net actuarial loss that will be amortized from AOCL into benefits cost in 2016			(6)
Estimated prior service credit that will be amortized from AOCL into benefits cost in 2016			(44)
Postretirement benefits funded status			(288)	(356)
Company contributions to plan assets			2	$ 2
Amiens Restructuring Plan
Defined Benefit Plan Disclosure [Line Items]
Curtailment gains (charges)	$ 22
Minimum
Defined Benefit Plan Disclosure [Line Items]
Expected contribution to funded non-U.S. pension plans in 2016			50
Maximum
Defined Benefit Plan Disclosure [Line Items]
Expected contribution to funded non-U.S. pension plans in 2016			$ 75
Salaried Employees | U.S. Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Company contributions to plan assets		$ 868
Discretionary contributions to plan assets		$ 834