Segment Information (Geographic area information) (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
Revenues from External Customers and Long-Lived Assets [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
Rental equipment, net	9,600				7,824				9,600	7,824
Property and equipment, net	614				467				614	467
Goodwill and other intangibles, net	6,142				4,957				6,142	4,957
Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									7,387	6,076	5,252
Rental equipment, net	8,910				7,264				8,910	7,264
Property and equipment, net	559				425				559	425
Goodwill and other intangibles, net	5,665				4,642				5,665	4,642
Foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									660	565	510
Rental equipment, net	690				560				690	560
Property and equipment, net	55				42				55	42
Goodwill and other intangibles, net	$ 477				$ 315				477	315
Total equipment rentals
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									6,940	5,715	4,941
Total equipment rentals | Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									6,388	5,253	4,524
Total equipment rentals | Foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									552	462	417
Sales of rental equipment
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from contract with customer, excluding assessed tax									664	550	496
Sales of rental equipment | Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from contract with customer, excluding assessed tax									609	494	444
Sales of rental equipment | Foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from contract with customer, excluding assessed tax									55	56	52
Sales of new equipment
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from contract with customer, excluding assessed tax									208	178	144
Sales of new equipment | Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from contract with customer, excluding assessed tax									184	157	129
Sales of new equipment | Foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from contract with customer, excluding assessed tax									24	21	15
Contractor supplies sales
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from contract with customer, excluding assessed tax									91	80	79
Contractor supplies sales | Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from contract with customer, excluding assessed tax									80	70	68
Contractor supplies sales | Foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from contract with customer, excluding assessed tax									11	10	11
Service and other revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from contract with customer, excluding assessed tax									144	118	102
Service and other revenues | Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from contract with customer, excluding assessed tax									126	102	87
Service and other revenues | Foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from contract with customer, excluding assessed tax									$ 18	$ 16	$ 15