Recent Accounting Pronouncements Revenue recognition (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of Goods and Services Sold	$ 1,255	$ 1,183	$ 3,914	$ 3,449
Selling, General and Administrative Expense	(129)	(133)	(412)	(353)
Other (charges) gains, net	12	0	9	(57)
Operating Income (Loss)	374	229	1,075	617
Non-operating pension and other postretirement employee benefit (expense) income	(25)	(23)	(77)	(67)
Retained earnings	5,819		5,819			$ 4,920
Accounting Standards Update 2017-07 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of Goods and Services Sold		(2)		(6)
Selling, General and Administrative Expense		21		62
Other (charges) gains, net				(1)
Operating Income (Loss)		(23)		(67)
Non-operating pension and other postretirement employee benefit (expense) income		$ (23)		$ (67)
Accounting Standards Update 2016-01 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption					$ 1
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings					$ 1
Minimum [Member] | Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Liability	150		150
Operating Lease, Right-of-Use Asset	150		150
Maximum [Member] | Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Liability	200		200
Operating Lease, Right-of-Use Asset	$ 200		$ 200