Revenue Recognition (Revenue summarized by type and applicable accounting standard) (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
Disaggregation of Revenue [Line Items]
Owned equipment rentals									$ 5,946	$ 4,928	$ 4,273
Re-rent revenue									138	106	93
Revenues	$ 2,306	$ 2,116	$ 1,891	$ 1,734	$ 1,922	$ 1,766	$ 1,597	$ 1,356	8,047	6,641	5,762
Ancillary and Other Rental Revenues
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax									477	389	340
Other									379	292	235
Revenues									856	681	575
Total equipment rentals
Disaggregation of Revenue [Line Items]
Revenues									6,940	5,715	4,941
Sales of rental equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax									664	550	496
Sales of new equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax									208	178	144
Contractor supplies sales
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax									91	80	79
Service and other revenues
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax									144	118	102
Topic 840
Disaggregation of Revenue [Line Items]
Owned equipment rentals									5,946	4,928	4,273
Re-rent revenue									138	106	93
Revenues									6,371	5,262	4,552
Topic 840 | Ancillary and Other Rental Revenues
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax									0	0	0
Other									287	228	186
Revenues									287	228	186
Topic 840 | Total equipment rentals
Disaggregation of Revenue [Line Items]
Revenues									6,371	5,262	4,552
Topic 606
Disaggregation of Revenue [Line Items]
Revenues									1,676
Topic 606 | Ancillary and Other Rental Revenues
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax									477
Other									92
Revenues									569
Topic 606 | Total equipment rentals
Disaggregation of Revenue [Line Items]
Revenues									569
Topic 606 | Sales of rental equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax									664
Topic 606 | Sales of new equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax									208
Topic 606 | Contractor supplies sales
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax									91
Topic 606 | Service and other revenues
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax									$ 144
Topic 605
Disaggregation of Revenue [Line Items]
Revenues										1,379	1,210
Topic 605 | Ancillary and Other Rental Revenues
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax										389	340
Other										64	49
Revenues										453	389
Topic 605 | Total equipment rentals
Disaggregation of Revenue [Line Items]
Revenues										453	389
Topic 605 | Sales of rental equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax										550	496
Topic 605 | Sales of new equipment
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax										178	144
Topic 605 | Contractor supplies sales
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax										80	79
Topic 605 | Service and other revenues
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax										$ 118	$ 102