Accounting Policies - Components of Other Income, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Other components of net periodic benefit cost	$ (32)	$ 79	$ (30)
Net loss from investments	1	19	5
Other (income) expense, net	(31)	98	$ (25)
Non-cash pre-tax settlement charge	$ 3	$ 113