Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		$ 93		$ 68	$ 54
Acquired		2		14	6
Charged to Costs and Expenses		8	[1]	45	40
Charged to Revenue		34	[1]	0	0
Deductions	[2]	34		34	32
Balance at End of Period		103		93	68
Reserve for obsolescence and shrinkage
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		5		7	3
Acquired		4		1	2
Charged to Costs and Expenses		40		26	20
Charged to Revenue		0		0	0
Deductions	[3]	39		29	18
Balance at End of Period		10		5	7
Self-insurance reserve
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		106		100	94
Acquired		0		5	6
Charged to Costs and Expenses		180		144	122
Charged to Revenue		0		0	0
Deductions	[4]	165		143	122
Balance at End of Period		$ 121		$ 106	$ 100

[1] Amounts charged to cost and expenses reflect bad debt expenses recognized within selling, general and administrative expenses. The amounts charged to revenue primarily reflect doubtful accounts associated with lease revenues that were recognized as a reduction to equipment rentals revenue. In 2019, we adopted an updated lease accounting standard (see note 13 to the consolidated financial statements for further detail) that requires that we recognize doubtful accounts associated with lease revenues as a reduction to equipment rentals revenue. We adopted the updated lease accounting standard using a transition method that does not require application to periods prior to adoption.

[2] Represents write-offs of accounts, net of recoveries.

[3] Represents write-offs.

[4] Represents payments.