Segment Reporting - Summarized Financial Information for Company's Reportable Segments (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021		Jun. 30, 2020		Dec. 31, 2020
Segment Reporting Information [Line Items]
Rental revenues		$ 94,581	$ 85,629	$ 180,668		$ 175,135
Rental related services revenues		22,688	20,475	42,357		44,986
Sales and other revenues				44,605		47,005
Total revenues		146,435	137,673	267,630		267,126
Depreciation of rental equipment		23,159	21,583	44,414		43,221
Gross profit		65,867	63,232	122,948		124,888
Selling and administrative expenses		36,261	30,540	69,398		62,494
Income from operations		29,606	32,692	53,550		62,394
Interest (expense) income allocation				(4,040)		(4,836)
Income before provision for income taxes		27,347	30,625	49,453		57,239
Rental equipment acquisitions				190,747		57,721
Accounts receivable, net (period end)		140,909	125,940	140,909		125,940		$ 123,316
Rental equipment, at cost (period end)		1,694,094	1,546,823	1,694,094		1,546,823		1,530,841
Rental equipment, net book value (period end)		1,073,055	969,681	1,073,055		969,681		$ 938,116
Mobile Modular [Member]
Segment Reporting Information [Line Items]
Rental revenues				99,895		94,038
Rental related services revenues				30,258		32,607
Sales and other revenues				23,067		23,315
Total revenues		84,572	76,762	153,220		149,960
Depreciation of rental equipment				12,893		11,406
Gross profit				75,693		74,301
Selling and administrative expenses				41,839		34,275
Income from operations				33,854		40,026
Interest (expense) income allocation				(2,426)		(2,826)
Income before provision for income taxes				31,428		37,200
Rental equipment acquisitions				148,252		33,650
Accounts receivable, net (period end)		96,976	82,110	96,976		82,110
Rental equipment, at cost (period end)		1,019,697	892,339	1,019,697		892,339
Rental equipment, net book value (period end)		739,916	624,971	$ 739,916		$ 624,971
Utilization (period end)	[1]			76.30%		76.80%
Average utilization	[1]			75.70%		78.20%
TRS-RenTelco [Member]
Segment Reporting Information [Line Items]
Rental revenues				$ 55,136		$ 53,548
Rental related services revenues				1,450		1,496
Sales and other revenues				10,800		12,098
Total revenues		33,783	33,079	67,386		67,142
Depreciation of rental equipment				23,278		23,582
Gross profit				29,365		28,958
Selling and administrative expenses				12,371		12,236
Income from operations				16,994		16,722
Interest (expense) income allocation				(920)		(1,147)
Income before provision for income taxes				16,017		15,256
Rental equipment acquisitions				42,421		22,661
Accounts receivable, net (period end)		22,678	22,211	22,678		22,211
Rental equipment, at cost (period end)		360,720	337,987	360,720		337,987
Rental equipment, net book value (period end)		172,035	166,996	$ 172,035		$ 166,996
Utilization (period end)	[1]			66.90%		65.70%
Average utilization	[1]			67.70%		64.70%
Adler Tanks [Member]
Segment Reporting Information [Line Items]
Rental revenues				$ 25,637		$ 27,549
Rental related services revenues				10,649		10,883
Sales and other revenues				1,382		890
Total revenues		19,958	18,633	37,668		39,322
Depreciation of rental equipment				8,243		8,233
Gross profit				15,019		17,576
Selling and administrative expenses				12,520		13,177
Income from operations				2,499		4,399
Interest (expense) income allocation				(922)		(1,179)
Income before provision for income taxes				1,577		3,220
Rental equipment acquisitions				74		1,410
Accounts receivable, net (period end)		13,545	13,976	13,545		13,976
Rental equipment, at cost (period end)		313,677	316,497	313,677		316,497
Rental equipment, net book value (period end)		161,104	177,714	$ 161,104		$ 177,714
Utilization (period end)	[1]			45.80%		43.10%
Average utilization	[1]			42.10%		45.90%
Enviroplex [Member]
Segment Reporting Information [Line Items]
Sales and other revenues	[2]			$ 9,356		$ 10,702
Total revenues		8,122	9,199	9,356	[2]	10,702	[2]
Gross profit	[2]			2,871		4,053
Selling and administrative expenses	[2]			2,668		2,806
Income from operations	[2]			203		1,247
Interest (expense) income allocation	[2]			228		316
Income before provision for income taxes	[2]			431		1,563
Accounts receivable, net (period end)	[2]	$ 7,710	$ 7,643	$ 7,710		$ 7,643

[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 10,211 and $11,979 for the six months ended June 30, 2021 and 2020, respectively. There were $855 and $1,277 inter-segment sales to Mobile Modular in the six months ended June 30, 2021 and 2020, respectively, which required elimination in consolidation.