Restructuring and Other Charges - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Restructuring Cost and Reserve [Line Items]
Integration activities charges	$ 6	$ 92	$ 28	$ 140
Non-cash impairment charge	0	40	5	40
Accelerated amortization expense included within finance lease expense		7		45
Accelerated amortization expense		24		34
Employee Severance
Restructuring Cost and Reserve [Line Items]
Severance and other separation costs	5	37	18	77
Employee severance and other separation costs accrual	13	29	13	29	$ 27	$ 14
Share-based compensation costs	$ 1	$ 15	$ 5	$ 23