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Segment Information (Reconciliation to Consolidated Totals) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Gross profit	$ 965	$ 1,033	$ 911	$ 761	$ 998	$ 938	$ 782	$ 646	$ 3,670	$ 3,364	$ 2,769
Selling, general and administrative expenses									(1,092)	(1,038)	(903)
Merger related costs					(22)				(1)	(36)	(50)
Restructuring charge					$ (16)				(18)	(31)	(50)
Non-rental depreciation and amortization									(407)	(308)	(259)
Interest expense, net									(648)	(481)	(464)
Other income, net									10	6	5
Income before provision (benefit) for income taxes									1,514	1,476	1,048
Equipment rentals
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Gross profit									3,207	2,963	2,440
Other products and services
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Gross profit									$ 463	$ 401	$ 329