Accounting Policies - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales	$ (3,830)	$ (3,699)
Net income	(80)	(169)
Cost of goods sold	(2,976)	(2,760)
Selling, general and administrative expense	(591)	(576)
Other (income) expense	37	8
Net periodic defined benefits expense (reversal of expense), excluding service cost component	2	10
Cumulative effect of adoption of new accounting standards				$ (1)	$ 0
Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of goods sold		5
Selling, general and administrative expense		3
General and administrative expense		$ 3
Other (income) expense	9
Accounting Standards Update 2016-09 | Scenario, Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net periodic defined benefits expense (reversal of expense)			$ 35
Net periodic defined benefits expense (reversal of expense), corporate related costs			5
Net periodic defined benefits expense (reversal of expense), excluding service cost component			90
Net periodic defined benefits expense (reversal of expense), excluding service cost component, corporate related costs			$ 15
Accounting Standards Update 2016-16 | Deferred Income Taxes
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption of new accounting standards	7
Accounting Standards Update 2016-16 | Other assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption of new accounting standards	(5)
Accounting Standards Update 2016-16 | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption of new accounting standards	2
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales	1
Net income	$ 1