Schedule of Concentration Risk of Gross Accounts Receivable From Owned Fleet (Detail) - Accounts Receivable - Customer Concentration Risk	9 Months Ended	12 Months Ended
Sep. 30, 2021	Dec. 31, 2020
Customer A
Concentration Risk [Line Items]
Percentage of lease rental income	35.30%	30.30%
Customer B
Concentration Risk [Line Items]
Percentage of lease rental income	7.70%	10.30%
Customer C
Concentration Risk [Line Items]
Percentage of lease rental income	17.80%	12.90%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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