Segment Reporting - Summarized Financial Information for Company's Reportable Segments (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Rental revenues		$ 74,261	$ 67,978
Rental related services revenues		17,831	17,935
Sales and other revenues		12,993	8,924
Total revenues		105,085	94,837
Depreciation of rental equipment		17,777	17,379
Gross profit		50,170	43,670
Selling and administrative expenses		28,128	27,848
Income from operations		22,042	15,822
Interest (expense) income allocation		(2,992)	(2,789)
Income (loss) before provision for income taxes		19,018	13,259
Rental equipment acquisitions		24,692	20,552
Accounts receivable, net (period end)		98,092	92,552	$ 105,872
Rental equipment, at cost (period end)		1,359,360	1,331,019	1,347,533
Rental equipment, net book value (period end)		865,338	856,981	$ 862,320
Mobile Modular [Member]
Segment Reporting Information [Line Items]
Rental revenues		37,027	33,654
Rental related services revenues		11,934	11,588
Sales and other revenues		4,890	3,061
Total revenues		53,851	48,303
Depreciation of rental equipment		5,248	5,333
Gross profit		26,321	22,444
Selling and administrative expenses		14,012	13,800
Income from operations		12,309	8,644
Interest (expense) income allocation		(1,676)	(1,591)
Income (loss) before provision for income taxes		10,633	7,053
Rental equipment acquisitions		8,233	7,782
Accounts receivable, net (period end)		55,883	53,779
Rental equipment, at cost (period end)		779,839	773,597
Rental equipment, net book value (period end)		$ 544,707	$ 545,953
Utilization (period end)	[1]	76.90%	76.50%
Average utilization	[1]	77.30%	76.80%
TRS-RenTelco [Member]
Segment Reporting Information [Line Items]
Rental revenues		$ 21,529	$ 19,746
Rental related services revenues		807	658
Sales and other revenues		5,702	4,910
Total revenues		28,038	25,314
Depreciation of rental equipment		8,577	8,091
Gross profit		12,848	11,393
Selling and administrative expenses		5,618	5,689
Income from operations		7,230	5,704
Interest (expense) income allocation		(683)	(546)
Income (loss) before provision for income taxes		6,515	5,384
Rental equipment acquisitions		15,532	12,021
Accounts receivable, net (period end)		19,902	18,603
Rental equipment, at cost (period end)		269,043	248,291
Rental equipment, net book value (period end)		$ 114,799	$ 92,561
Utilization (period end)	[1]	63.50%	62.10%
Average utilization	[1]	62.70%	62.20%
Adler Tanks [Member]
Segment Reporting Information [Line Items]
Rental revenues		$ 15,705	$ 14,578
Rental related services revenues		5,090	5,689
Sales and other revenues		383	194
Total revenues		21,178	20,461
Depreciation of rental equipment		3,952	3,955
Gross profit		10,396	9,555
Selling and administrative expenses		7,198	7,267
Income from operations		3,198	2,288
Interest (expense) income allocation		(775)	(738)
Income (loss) before provision for income taxes		2,423	1,550
Rental equipment acquisitions		927	749
Accounts receivable, net (period end)		16,490	15,814
Rental equipment, at cost (period end)		310,478	309,131
Rental equipment, net book value (period end)		$ 205,832	$ 218,467
Utilization (period end)	[1]	57.50%	53.40%
Average utilization	[1]	57.60%	52.30%
Enviroplex [Member]
Segment Reporting Information [Line Items]
Sales and other revenues	[2]	$ 2,018	$ 759
Total revenues	[2]	2,018	759
Gross profit	[2]	605	278
Selling and administrative expenses	[2]	1,300	1,092
Income from operations	[2]	(695)	(814)
Interest (expense) income allocation	[2]	142	86
Income (loss) before provision for income taxes	[2]	(553)	(728)
Accounts receivable, net (period end)	[2]	$ 5,817	$ 4,356

[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 $2,813 and $759 for the three months ended March 31, 2018 and 2017, respectively. There were $795 inter-segment sales to Mobile Modular in the three months ended March 31, 2018 requiring elimination in consolidation. There were no inter-segment sales in the three months ended March 31, 2017.