Acquisitions (Purchase Price Allocation - Neff Acquisition) (Details) - USD ($) $ in Millions	1 Months Ended
	Oct. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill		$ 4,082	$ 3,260	$ 3,243	$ 3,272
Neff Corporation
Business Acquisition [Line Items]
Accounts receivable, net of allowance for doubtful accounts	$ 72
Inventory	5
Rental equipment	551
Property and equipment	45
Intangibles (customer relationships)	153
Other assets	5
Total identifiable assets acquired	831
Current liabilities	(61)
Deferred taxes	(35)
Other long-term liabilities	(3)
Total liabilities assumed	(99)
Net identifiable assets acquired	732
Goodwill	584
Net assets acquired	1,316
Accounts receivable, gross	74
Accounts receivable, allowance for doubtful accounts	2
Goodwill expected to be deductible for tax purposes	$ 12
Customer relationships | Neff Corporation
Business Acquisition [Line Items]
Life (years)	10 years