Segment Reporting - Summarized Financial Information for Company's Reportable Segments (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Rental revenues		$ 73,781	$ 67,757	$ 211,712	$ 201,036
Rental related services revenues		21,856	20,122	58,587	57,028
Sales and other revenues				69,508	60,733
Total revenues		135,388	121,993	339,807	318,797
Depreciation of rental equipment		17,492	17,819	52,113	54,590
Gross profit		58,775	50,433	151,656	134,844
Selling and administrative expenses		28,489	26,201	83,702	78,281
Income from operations		30,286	24,232	67,954	56,563
Interest (expense) income allocation				(8,724)	(9,486)
Income before provision for income taxes		27,336	21,277	59,503	47,136
Rental equipment acquisitions				76,937	60,758
Accounts receivable, net (period end)		107,413	104,004	107,413	104,004	$ 96,877
Rental equipment, at cost (period end)		1,350,493	1,325,202	1,350,493	1,325,202	1,324,057
Rental equipment, net book value (period end)		865,724	862,528	865,724	862,528	$ 856,371
Mobile Modular [Member]
Segment Reporting Information [Line Items]
Rental revenues				104,923	96,002
Rental related services revenues				38,283	37,034
Sales and other revenues				30,622	25,416
Total revenues				173,828	158,452
Depreciation of rental equipment				15,951	15,642
Gross profit				77,939	67,329
Selling and administrative expenses				42,157	38,162
Income from operations				35,782	29,167
Interest (expense) income allocation				(5,008)	(5,264)
Income before provision for income taxes				30,774	23,903
Rental equipment acquisitions				28,107	35,363
Accounts receivable, net (period end)		66,126	63,752	66,126	63,752
Rental equipment, at cost (period end)		781,791	763,777	781,791	763,777
Rental equipment, net book value (period end)		547,115	543,141	$ 547,115	$ 543,141
Utilization (period end)	[1]			76.80%	77.60%
Average utilization	[1]			76.60%	76.30%
TRS-RenTelco [Member]
Segment Reporting Information [Line Items]
Rental revenues				$ 60,569	$ 61,562
Rental related services revenues				2,095	2,156
Sales and other revenues				16,493	18,491
Total revenues				79,157	82,209
Depreciation of rental equipment				24,335	26,939
Gross profit				36,420	34,033
Selling and administrative expenses				16,475	16,444
Income from operations				19,945	17,589
Interest (expense) income allocation				(1,726)	(1,921)
Income before provision for income taxes				18,492	15,727
Rental equipment acquisitions				45,700	24,991
Accounts receivable, net (period end)		16,253	20,267	16,253	20,267
Rental equipment, at cost (period end)		258,877	252,573	258,877	252,573
Rental equipment, net book value (period end)		106,728	93,894	$ 106,728	$ 93,894
Utilization (period end)	[1]			64.30%	62.40%
Average utilization	[1]			62.80%	60.10%
Adler Tanks [Member]
Segment Reporting Information [Line Items]
Rental revenues				$ 46,220	$ 43,472
Rental related services revenues				18,209	17,838
Sales and other revenues				1,701	1,039
Total revenues				66,130	62,349
Depreciation of rental equipment				11,827	12,009
Gross profit				31,407	28,362
Selling and administrative expenses				21,855	20,786
Income from operations				9,552	7,576
Interest (expense) income allocation				(2,301)	(2,487)
Income before provision for income taxes				7,251	5,089
Rental equipment acquisitions				3,130	404
Accounts receivable, net (period end)		18,118	15,922	18,118	15,922
Rental equipment, at cost (period end)		309,825	308,852	309,825	308,852
Rental equipment, net book value (period end)		211,881	225,493	$ 211,881	$ 225,493
Utilization (period end)	[1]			59.70%	52.10%
Average utilization	[1]			54.70%	49.90%
Enviroplex [Member]
Segment Reporting Information [Line Items]
Sales and other revenues	[2]			$ 20,692	$ 15,787
Total revenues	[2]			20,692	15,787
Gross profit	[2]			5,890	5,120
Selling and administrative expenses	[2]			3,215	2,889
Income from operations	[2]			2,675	2,231
Interest (expense) income allocation	[2]			311	186
Income before provision for income taxes	[2]			2,986	2,417
Accounts receivable, net (period end)	[2]	$ 6,916	$ 4,063	$ 6,916	$ 4,063

[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 $20,692 and $15,872 for the nine months ended September 30, 2017 and 2016, respectively, with no intercompany sales to Mobile Modular in 2017 and $85 inter-segment sales to Mobile Modular in 2016, which were eliminated in consolidation.