Segment Reporting - Summarized Financial Information for Company's Reportable Segments (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019		Jun. 30, 2018		Dec. 31, 2018
Segment Reporting Information [Line Items]
Rental revenues		$ 88,105	$ 77,267	$ 170,801		$ 151,528
Rental related services revenues		24,467	19,086	45,922		36,917
Sales and other revenues				32,724		33,623
Total revenues		127,439	116,983	249,447		222,068
Depreciation of rental equipment		19,726	18,103	38,687		35,880
Gross profit		59,881	53,928	116,886		104,098
Selling and administrative expenses		30,815	29,479	60,510		57,607
Income from operations		29,066	24,449	56,376		46,491
Interest (expense) income allocation				(6,246)		(5,991)
Income (loss) before provision for income taxes		25,965	21,106	50,216		40,124
Rental equipment acquisitions				89,940		59,458
Accounts receivable, net (period end)		121,018	105,095	121,018		105,095		$ 121,016
Rental equipment, at cost (period end)		1,477,286	1,379,579	1,477,286		1,379,579		1,416,000
Rental equipment, net book value (period end)		943,152	876,522	943,152		876,522		$ 901,015
Mobile Modular [Member]
Segment Reporting Information [Line Items]
Rental revenues				86,998		75,231
Rental related services revenues				30,372		24,322
Sales and other revenues				15,444		14,169
Total revenues		67,722	59,871	132,814		113,722
Depreciation of rental equipment				10,877		10,521
Gross profit				62,865		53,050
Selling and administrative expenses				31,047		28,930
Income from operations				31,818		24,120
Interest (expense) income allocation				(3,761)		(3,422)
Income (loss) before provision for income taxes				28,057		20,698
Rental equipment acquisitions				43,614		22,287
Accounts receivable, net (period end)		75,633	63,003	75,633		63,003
Rental equipment, at cost (period end)		854,076	789,158	854,076		789,158
Rental equipment, net book value (period end)		600,351	550,285	$ 600,351		$ 550,285
Utilization (period end)	[1]			79.60%		77.20%
Average utilization	[1]			79.10%		77.30%
TRS-RenTelco [Member]
Segment Reporting Information [Line Items]
Rental revenues				$ 49,112		$ 43,694
Rental related services revenues				1,562		1,514
Sales and other revenues				12,312		13,182
Total revenues		32,310	30,352	62,986		58,390
Depreciation of rental equipment				19,684		17,443
Gross profit				28,492		27,242
Selling and administrative expenses				12,063		11,560
Income from operations				16,429		15,682
Interest (expense) income allocation				(1,385)		(1,313)
Income (loss) before provision for income taxes				15,130		13,993
Rental equipment acquisitions				42,999		34,502
Accounts receivable, net (period end)		21,212	18,391	21,212		18,391
Rental equipment, at cost (period end)		307,639	278,253	307,639		278,253
Rental equipment, net book value (period end)		150,655	122,647	$ 150,655		$ 122,647
Utilization (period end)	[1]			67.30%		62.80%
Average utilization	[1]			65.70%		62.80%
Adler Tanks [Member]
Segment Reporting Information [Line Items]
Rental revenues				$ 34,691		$ 32,603
Rental related services revenues				13,988		11,081
Sales and other revenues				1,091		543
Total revenues		26,335	23,049	49,770		44,227
Depreciation of rental equipment				8,126		7,916
Gross profit				24,086		21,912
Selling and administrative expenses				14,894		14,658
Income from operations				9,192		7,254
Interest (expense) income allocation				(1,646)		(1,576)
Income (loss) before provision for income taxes				7,546		5,678
Rental equipment acquisitions				3,327		2,669
Accounts receivable, net (period end)		20,106	18,239	20,106		18,239
Rental equipment, at cost (period end)		315,571	312,168	315,571		312,168
Rental equipment, net book value (period end)		192,146	203,590	$ 192,146		$ 203,590
Utilization (period end)	[1]			55.30%		61.30%
Average utilization	[1]			57.10%		58.50%
Enviroplex [Member]
Segment Reporting Information [Line Items]
Sales and other revenues	[2]			$ 3,877		$ 5,729
Total revenues		1,072	3,711	3,877	[2]	5,729	[2]
Gross profit	[2]			1,443		1,894
Selling and administrative expenses	[2]			2,506		2,459
Income from operations	[2]			(1,063)		(565)
Interest (expense) income allocation	[2]			546		320
Income (loss) before provision for income taxes	[2]			(517)		(245)
Accounts receivable, net (period end)	[2]	$ 4,067	$ 5,462	$ 4,067		$ 5,462

[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 $3,877 and $6,524 for the six months ended June 30, 2019 and 2018, respectively. There were $795 inter-segment sales to Mobile Modular in the six months ended June 30, 2018, which required elimination in consolidation.  There were no inter-segment sales in the six months ended June 30, 2019.