Segment Reporting - Summarized Financial Information for Company's Reportable Segments (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021		Sep. 30, 2020		Dec. 31, 2020
Segment Reporting Information [Line Items]
Rental revenues		$ 103,269	$ 88,138	$ 283,937		$ 263,273
Rental related services revenues		31,513	25,040	73,870		70,026
Sales and other revenues				83,115		90,275
Total revenues		173,292	156,448	440,922		423,574
Depreciation of rental equipment		23,802	21,419	68,216		64,640
Gross profit		75,805	68,204	198,753		193,093
Selling and administrative expenses		39,907	30,871	109,305		93,365
Income from operations		35,898	37,333	89,448		99,728
Interest (expense) income allocation				(7,208)		(6,804)
Income before provision for income taxes		32,602	35,495	82,055		92,735
Rental equipment acquisitions				215,904		64,990
Accounts receivable, net (period end)		168,831	129,433	168,831		129,433		$ 123,316
Rental equipment, at cost (period end)		1,698,820	1,536,944	1,698,820		1,536,944		1,530,841
Rental equipment, net book value (period end)		1,063,462	948,125	1,063,462		948,125		$ 938,116
Mobile Modular [Member]
Segment Reporting Information [Line Items]
Rental revenues				159,118		141,172
Rental related services revenues				54,726		51,291
Sales and other revenues				49,770		52,910
Total revenues		110,394	95,413	263,614		245,373
Depreciation of rental equipment				20,437		17,177
Gross profit				125,357		116,928
Selling and administrative expenses				67,977		52,014
Income from operations				57,380		64,914
Interest (expense) income allocation				(4,401)		(3,982)
Income before provision for income taxes				52,979		60,932
Rental equipment acquisitions				162,579		31,667
Accounts receivable, net (period end)		118,467	85,033	118,467		85,033
Rental equipment, at cost (period end)		1,023,344	885,314	1,023,344		885,314
Rental equipment, net book value (period end)		737,807	613,357	$ 737,807		$ 613,357
Utilization (period end)	[1]			76.70%		76.50%
Average utilization	[1]			76.00%		77.50%
TRS-RenTelco [Member]
Segment Reporting Information [Line Items]
Rental revenues				$ 84,340		$ 81,167
Rental related services revenues				2,149		2,296
Sales and other revenues				15,971		19,535
Total revenues		35,074	35,856	102,460		102,998
Depreciation of rental equipment				35,429		35,129
Gross profit				44,867		43,921
Selling and administrative expenses				18,381		18,198
Income from operations				26,486		25,723
Interest (expense) income allocation				(1,588)		(1,606)
Income before provision for income taxes				24,713		23,928
Rental equipment acquisitions				53,161		31,643
Accounts receivable, net (period end)		24,854	23,758	24,854		23,758
Rental equipment, at cost (period end)		363,799	335,520	363,799		335,520
Rental equipment, net book value (period end)		169,250	161,120	$ 169,250		$ 161,120
Utilization (period end)	[1]			66.90%		68.40%
Average utilization	[1]			67.40%		65.60%
Adler Tanks [Member]
Segment Reporting Information [Line Items]
Rental revenues				$ 40,479		$ 40,934
Rental related services revenues				16,995		16,439
Sales and other revenues				2,477		1,214
Total revenues		22,283	19,265	59,951		58,587
Depreciation of rental equipment				12,350		12,334
Gross profit				24,167		26,116
Selling and administrative expenses				18,853		18,998
Income from operations				5,314		7,118
Interest (expense) income allocation				(1,560)		(1,651)
Income before provision for income taxes				3,754		5,467
Rental equipment acquisitions				164		1,680
Accounts receivable, net (period end)		16,062	14,567	16,062		14,567
Rental equipment, at cost (period end)		311,677	316,110	311,677		316,110
Rental equipment, net book value (period end)		156,405	173,648	$ 156,405		$ 173,648
Utilization (period end)	[1]			50.40%		45.50%
Average utilization	[1]			44.00%		45.50%
Enviroplex [Member]
Segment Reporting Information [Line Items]
Sales and other revenues	[2]			$ 14,897		$ 16,616
Total revenues		5,541	5,914	14,897	[2]	16,616	[2]
Gross profit	[2]			4,362		6,128
Selling and administrative expenses	[2]			4,094		4,155
Income from operations	[2]			268		1,973
Interest (expense) income allocation	[2]			341		435
Income before provision for income taxes	[2]			609		2,408
Accounts receivable, net (period end)	[2]	$ 9,448	$ 6,075	$ 9,448		$ 6,075

[1] Utilization is calculated each month by dividing the cost of rental equipment on rent by the total cost of rental equipment, excluding accessory equipment, and for Mobile Modular and Adler Tanks, excluding new equipment inventory.  The Average utilization for the period is calculated using the average costs of rental equipment.

[2] Gross Enviroplex sales revenues were $15,909 and $17,892 for the nine months ended September 30, 2021 and 2020, respectively. There were $1,012 and $1,276 inter-segment sales to Mobile Modular in the nine months ended September 30, 2021 and 2020, respectively, which required elimination in consolidation.