Segment Information (Financial information by segment) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 2,306	$ 2,116	$ 1,891	$ 1,734	$ 1,922	$ 1,766	$ 1,597	$ 1,356	$ 8,047	$ 6,641	$ 5,762
Depreciation and amortization									1,671	1,383	1,245
Gross profit	998	$ 938	$ 782	$ 646	827	$ 773	$ 655	$ 514	3,364	2,769	2,403
Capital expenditures									2,291	1,889	1,339
Total assets	18,133				15,030				18,133	15,030	11,988
General rentals
Segment Reporting Information [Line Items]
Revenues									6,550	5,565	4,908
Depreciation and amortization									1,410	1,188	1,066
Capital expenditures									1,980	1,675	1,189
Total assets	15,597				13,351				15,597	13,351	10,496
Trench, power and fluid solutions
Segment Reporting Information [Line Items]
Revenues									1,497	1,076	854
Depreciation and amortization									261	195	179
Capital expenditures									311	214	150
Total assets	$ 2,536				$ 1,679				2,536	1,679	1,492
Total equipment rentals
Segment Reporting Information [Line Items]
Revenues									6,940	5,715	4,941
Total equipment rentals | General rentals
Segment Reporting Information [Line Items]
Revenues									5,550	4,727	4,166
Total equipment rentals | Trench, power and fluid solutions
Segment Reporting Information [Line Items]
Revenues									1,390	988	775
Sales of rental equipment
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax									664	550	496
Sales of rental equipment | General rentals
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax									619	509	459
Sales of rental equipment | Trench, power and fluid solutions
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax									45	41	37
Sales of new equipment
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax									208	178	144
Sales of new equipment | General rentals
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax									186	159	128
Sales of new equipment | Trench, power and fluid solutions
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax									22	19	16
Contractor supplies sales
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax									91	80	79
Contractor supplies sales | General rentals
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax									68	65	64
Contractor supplies sales | Trench, power and fluid solutions
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax									23	15	15
Service and other revenues
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax									144	118	102
Service and other revenues | General rentals
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax									127	105	91
Service and other revenues | Trench, power and fluid solutions
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax									17	13	11
Equipment rentals
Segment Reporting Information [Line Items]
Gross profit									2,963	2,440	2,089
Equipment rentals | General rentals
Segment Reporting Information [Line Items]
Gross profit									2,293	1,950	1,725
Equipment rentals | Trench, power and fluid solutions
Segment Reporting Information [Line Items]
Gross profit									$ 670	$ 490	$ 364