Segment Information (Reconciliation to Consolidated Totals) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Gross profit	$ 869	$ 886	$ 701	$ 727	$ 965	$ 1,033	$ 911	$ 761	$ 3,183	$ 3,670	$ 3,364
Selling, general and administrative expenses									(979)	(1,092)	(1,038)
Merger related costs									0	(1)	(36)
Restructuring charge									(17)	(18)	(31)
Non-rental depreciation and amortization									(387)	(407)	(308)
Interest expense, net									(669)	(648)	(481)
Other income, net									8	10	6
Income before provision (benefit) for income taxes									1,139	1,514	1,476
Equipment rentals
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Gross profit									2,719	3,207	2,963
Other products and services
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Gross profit									$ 464	$ 463	$ 401