Segment Reporting - Summarized Financial Information for Company's Reportable Segments (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019		Sep. 30, 2018		Dec. 31, 2018
Segment Reporting Information [Line Items]
Rental revenues		$ 90,857	$ 82,155	$ 261,658		$ 233,683
Rental related services revenues		30,816	23,880	76,738		60,797
Sales and other revenues				84,613		70,735
Total revenues		173,562	143,147	423,009		365,215
Depreciation of rental equipment		20,535	18,407	59,222		54,287
Gross profit		78,282	64,050	195,168		168,148
Selling and administrative expenses		31,534	28,226	92,044		85,833
Income from operations		46,748	35,824	103,124		82,315
Interest (expense) income allocation				(9,407)		(9,133)
Income before provision for income taxes		43,455	32,553	93,671		72,677
Rental equipment acquisitions				132,493		95,635
Accounts receivable, net (period end)		138,114	115,089	138,114		115,089		$ 121,016
Rental equipment, at cost (period end)		1,502,769	1,398,263	1,502,769		1,398,263		1,416,000
Rental equipment, net book value (period end)		958,610	888,607	958,610		888,607		$ 901,015
Mobile Modular [Member]
Segment Reporting Information [Line Items]
Rental revenues				133,736		116,436
Rental related services revenues				52,946		40,510
Sales and other revenues				32,434		31,667
Total revenues		86,302	74,891	219,116		188,613
Depreciation of rental equipment				16,449		15,841
Gross profit				102,029		86,515
Selling and administrative expenses				48,013		43,191
Income from operations				54,016		43,324
Interest (expense) income allocation				(5,948)		(5,256)
Income before provision for income taxes				48,068		38,068
Rental equipment acquisitions				62,084		40,704
Accounts receivable, net (period end)		88,893	69,419	88,893		69,419
Rental equipment, at cost (period end)		865,254	801,129	865,254		801,129
Rental equipment, net book value (period end)		607,949	558,790	$ 607,949		$ 558,790
Utilization (period end)	[1]			79.50%		79.20%
Average utilization	[1]			79.10%		77.80%
TRS-RenTelco [Member]
Segment Reporting Information [Line Items]
Rental revenues				$ 76,050		$ 65,919
Rental related services revenues				2,425		2,287
Sales and other revenues				18,601		18,321
Total revenues		34,090	28,137	97,076		86,527
Depreciation of rental equipment				30,533		26,536
Gross profit				44,673		40,155
Selling and administrative expenses				18,101		16,780
Income from operations				26,572		23,375
Interest (expense) income allocation				(1,662)		(1,999)
Income before provision for income taxes				24,864		20,871
Rental equipment acquisitions				66,525		51,744
Accounts receivable, net (period end)		22,515	18,991	22,515		18,991
Rental equipment, at cost (period end)		321,677	284,647	321,677		284,647
Rental equipment, net book value (period end)		162,196	129,816	$ 162,196		$ 129,816
Utilization (period end)	[1]			67.10%		61.50%
Average utilization	[1]			66.00%		62.40%
Adler Tanks [Member]
Segment Reporting Information [Line Items]
Rental revenues				$ 51,872		$ 51,328
Rental related services revenues				21,367		18,000
Sales and other revenues				1,340		916
Total revenues		24,809	26,017	74,579		70,244
Depreciation of rental equipment				12,240		11,910
Gross profit				36,380		35,031
Selling and administrative expenses				22,054		22,245
Income from operations				14,326		12,786
Interest (expense) income allocation				(2,598)		(2,409)
Income before provision for income taxes				11,728		10,377
Rental equipment acquisitions				3,884		3,187
Accounts receivable, net (period end)		19,382	19,876	19,382		19,876
Rental equipment, at cost (period end)		315,838	312,487	315,838		312,487
Rental equipment, net book value (period end)		188,465	200,001	$ 188,465		$ 200,001
Utilization (period end)	[1]			51.00%		64.00%
Average utilization	[1]			56.20%		59.80%
Enviroplex [Member]
Segment Reporting Information [Line Items]
Sales and other revenues	[2]			$ 32,238		$ 19,831
Total revenues		28,361	14,102	32,238	[2]	19,831	[2]
Gross profit	[2]			12,086		6,447
Selling and administrative expenses	[2]			3,876		3,617
Income from operations	[2]			8,210		2,830
Interest (expense) income allocation	[2]			801		531
Income before provision for income taxes	[2]			9,011		3,361
Accounts receivable, net (period end)	[2]	$ 7,324	$ 6,803	$ 7,324		$ 6,803

[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 $32,238 and $21,191 for the nine months ended September 30, 2019 and 2018, respectively. There were $1,360 inter-segment sales to Mobile Modular in the nine months ended September 30, 2018, which required elimination in consolidation.  There were no inter-segment sales in the nine months ended September 30, 2019.