Nature of Operations and Basis of Presentation - Components of Other (Income) Expense, Net (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other (income) expense, net	$ (6)		$ (11)	$ 97	$ (16)
Non-cash pre-tax settlement charge		$ 113
Accounting Standards Update 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other components of net periodic benefit cost	(7)		(8)	96	(16)
Net loss (gain) from investments	1		(3)	1	0
Other (income) expense, net	$ (6)		$ (11)	$ 97	$ (16)