Accounting Policies - Components of Other Income, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Non-Cash Settlement Charge of Unamortized Actuarial Loss, before Tax	$ 113
Other income, net	98	$ (25)	$ (27)
Accounting Standards Update 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other components of net periodic benefit cost 1	79	(30)	(27)
Net loss from investments	19	5	0
Other income, net	$ 98	$ (25)	$ (27)