Segment Information (Geographic area information) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Equipment rentals									$ 5,715	$ 4,941	$ 4,949
Service and other revenues									118	102	94
Total revenues	$ 1,922	$ 1,766	$ 1,597	$ 1,356	$ 1,523	$ 1,508	$ 1,421	$ 1,310	6,641	5,762	5,817
Rental equipment, net	7,824				6,189				7,824	6,189
Property and equipment, net	467				430				467	430
Goodwill and other intangibles, net	4,957				4,002				4,957	4,002
Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Equipment rentals									5,253	4,524	4,452
Service and other revenues									102	87	80
Total revenues									6,076	5,252	5,218
Rental equipment, net	7,264				5,709				7,264	5,709
Property and equipment, net	425				390				425	390
Goodwill and other intangibles, net	4,642				3,699				4,642	3,699
Foreign (Canada)
Revenues from External Customers and Long-Lived Assets [Line Items]
Equipment rentals									462	417	497
Service and other revenues									16	15	14
Total revenues									565	510	599
Rental equipment, net	560				480				560	480
Property and equipment, net	42				40				42	40
Goodwill and other intangibles, net	$ 315				$ 303				315	303
Rental Equipment
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales revenue									550	496	538
Rental Equipment | Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales revenue									494	444	480
Rental Equipment | Foreign (Canada)
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales revenue									56	52	58
New Equipment
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales revenue									178	144	157
New Equipment | Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales revenue									157	129	137
New Equipment | Foreign (Canada)
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales revenue									21	15	20
Contractor Supplies
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales revenue									80	79	79
Contractor Supplies | Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales revenue									70	68	69
Contractor Supplies | Foreign (Canada)
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales revenue									$ 10	$ 11	$ 10