Significant Accounting Policies - Additional Information (Detail)	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2020 USD ($) Customer	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 Customer	Sep. 30, 2020 USD ($) Customer Segment	Sep. 30, 2019 Customer	Dec. 31, 2019 USD ($) Customer	Dec. 31, 2018 USD ($)
Summary Of Significant Accounting Policy [Line Items]
Customer accounted for more than 10% of revenue | Customer	0			0	0	0	0
Number of operating segments | Segment					6
Goodwill impairment					$ 61,994,000
Goodwill	$ 68,851,000		$ 131,442,000		$ 68,851,000		$ 131,442,000	$ 105,843,000
Topic 326 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in accounting principle, accounting standards update, adopted	true				true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020				Jan. 01, 2020
Change in accounting principle, accounting standards update, immaterial effect	true				true
Accounting Standards Update 2018-13 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in accounting principle, accounting standards update, adopted	true				true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020				Jan. 01, 2020
Change in accounting principle, accounting standards update, immaterial effect	true				true
New Equipment Sales [Member]
Summary Of Significant Accounting Policy [Line Items]
Goodwill impairment			10,700,000
Goodwill			0				0	10,434,000
Service Revenues [Member]
Summary Of Significant Accounting Policy [Line Items]
Goodwill impairment			1,500,000
Goodwill			0				0
Equipment Rental Component 2 [Member]
Summary Of Significant Accounting Policy [Line Items]
Goodwill impairment		$ 62,000,000.0
Goodwill			62,311,000				62,311,000	42,536,000
Equipment Rental Component 1 [Member]
Summary Of Significant Accounting Policy [Line Items]
Goodwill	$ 48,976,000		49,215,000		$ 48,976,000		49,215,000	34,297,000
Reporting units, percentage of fair value that exceeded respective carrying value		34.00%
Used Equipment Sales [Member]
Summary Of Significant Accounting Policy [Line Items]
Goodwill	8,953,000		8,961,000		8,953,000		8,961,000	8,461,000
Reporting units, percentage of fair value that exceeded respective carrying value		90.00%
Parts Sales [Member]
Summary Of Significant Accounting Policy [Line Items]
Goodwill	$ 10,922,000		$ 10,955,000		$ 10,922,000		$ 10,955,000	$ 8,910,000
Reporting units, percentage of fair value that exceeded respective carrying value		40.00%