Segment Reporting - Summarized Financial Information for Company's Reportable Segments (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018		Jun. 30, 2017		Dec. 31, 2017
Segment Reporting Information [Line Items]
Rental revenues		$ 77,267	$ 69,953	$ 151,528		$ 137,931
Rental related services revenues		19,086	18,796	36,917		36,731
Sales and other revenues				33,623		29,757
Total revenues		116,983	109,582	222,068		204,419
Depreciation of rental equipment		18,103	17,242	35,880		34,621
Gross profit		53,928	49,211	104,098		92,881
Selling and administrative expenses		29,479	27,365	57,607		55,213
Income from operations		24,449	21,846	46,491		37,668
Interest (expense) income allocation				(5,991)		(5,738)
Income (loss) before provision for income taxes		21,106	18,908	40,124		32,167
Rental equipment acquisitions				59,458		49,599
Accounts receivable, net (period end)		105,095	96,539	105,095		96,539		$ 105,872
Rental equipment, at cost (period end)		1,379,579	1,342,222	1,379,579		1,342,222		1,347,533
Rental equipment, net book value (period end)		876,522	863,207	876,522		863,207		$ 862,320
Mobile Modular [Member]
Segment Reporting Information [Line Items]
Rental revenues				75,231		68,684
Rental related services revenues				24,322		23,554
Sales and other revenues				14,169		12,703
Total revenues		59,871	56,638	113,722		104,941
Depreciation of rental equipment				10,521		10,666
Gross profit				53,050		47,578
Selling and administrative expenses				28,930		27,617
Income from operations				24,120		19,961
Interest (expense) income allocation				(3,422)		(3,289)
Income (loss) before provision for income taxes				20,698		16,672
Rental equipment acquisitions				22,287		21,531
Accounts receivable, net (period end)		63,003	57,268	63,003		57,268
Rental equipment, at cost (period end)		789,158	782,503	789,158		782,503
Rental equipment, net book value (period end)		550,285	551,101	$ 550,285		$ 551,101
Utilization (period end)	[1]			77.20%		75.70%
Average utilization	[1]			77.30%		76.60%
TRS-RenTelco [Member]
Segment Reporting Information [Line Items]
Rental revenues				$ 43,694		$ 39,551
Rental related services revenues				1,514		1,312
Sales and other revenues				13,182		10,990
Total revenues		30,352	26,539	58,390		51,853
Depreciation of rental equipment				17,443		16,071
Gross profit				27,242		23,847
Selling and administrative expenses				11,560		11,019
Income from operations				15,682		12,828
Interest (expense) income allocation				(1,313)		(1,126)
Income (loss) before provision for income taxes				13,993		11,939
Rental equipment acquisitions				34,502		25,510
Accounts receivable, net (period end)		18,391	18,443	18,391		18,443
Rental equipment, at cost (period end)		278,253	249,935	278,253		249,935
Rental equipment, net book value (period end)		122,647	96,547	$ 122,647		$ 96,547
Utilization (period end)	[1]			62.80%		61.60%
Average utilization	[1]			62.80%		62.30%
Adler Tanks [Member]
Segment Reporting Information [Line Items]
Rental revenues				$ 32,603		$ 29,696
Rental related services revenues				11,081		11,865
Sales and other revenues				543		1,153
Total revenues		23,049	22,253	44,227		42,714
Depreciation of rental equipment				7,916		7,884
Gross profit				21,912		19,832
Selling and administrative expenses				14,658		14,528
Income from operations				7,254		5,304
Interest (expense) income allocation				(1,576)		(1,515)
Income (loss) before provision for income taxes				5,678		3,789
Rental equipment acquisitions				2,669		2,558
Accounts receivable, net (period end)		18,239	15,918	18,239		15,918
Rental equipment, at cost (period end)		312,168	309,784	312,168		309,784
Rental equipment, net book value (period end)		203,590	215,559	$ 203,590		$ 215,559
Utilization (period end)	[1]			61.30%		55.40%
Average utilization	[1]			58.50%		53.40%
Enviroplex [Member]
Segment Reporting Information [Line Items]
Sales and other revenues	[2]			$ 5,729		$ 4,911
Total revenues		3,711	4,152	5,729	[2]	4,911	[2]
Gross profit	[2]			1,894		1,624
Selling and administrative expenses	[2]			2,459		2,049
Income from operations	[2]			(565)		(425)
Interest (expense) income allocation	[2]			320		192
Income (loss) before provision for income taxes	[2]			(245)		(233)
Accounts receivable, net (period end)	[2]	$ 5,462	$ 4,910	$ 5,462		$ 4,910

[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 $6,524 and $4,911 for the six months ended June 30, 2018 and 2017, 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, 2017.