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Revenue Recognition (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Contract with customer, liability	$ 51		$ 51
Accounts receivable, net	1,254		1,315
Allowance for doubtful accounts	104		$ 108
Contract with customer, asset	0
Revenue recognized	0	$ 0
Contract with customer, performance obligation satisfied in previous period	$ 0	$ 0
Accounts Receivable \| Customer concentration risk
Property, Plant and Equipment [Line Items]
Concentration risk	1.00%		2.00%
Revenues \| Product concentration risk
Property, Plant and Equipment [Line Items]
Concentration risk	74.00%
Revenues \| Largest customer \| Customer concentration risk
Property, Plant and Equipment [Line Items]
Concentration risk	1.00%		1.00%	1.00%	1.00%
Owned equipment rentals \| Revenues \| Product concentration risk
Property, Plant and Equipment [Line Items]
Concentration risk	68.00%
US \| Revenues \| Geographic Concentration Risk
Property, Plant and Equipment [Line Items]
Concentration risk	91.00%
General rentals \| Revenues \| Product concentration risk
Property, Plant and Equipment [Line Items]
Concentration risk	79.00%