Segment Reporting - Summarized Financial Information for Company's Reportable Segments (Detail) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Rental revenues		$ 92,231	$ 90,857	$ 88,105	$ 82,696	$ 85,091	$ 82,155	$ 77,267	$ 74,261	$ 353,889	$ 318,774	$ 289,417
Rental related services revenues										101,038	82,907	78,068
Sales and other revenues										115,303	96,649	94,549
Total revenues		147,221	173,562	127,439	122,008	133,115	143,147	116,983	105,085	570,230	498,330	462,034
Depreciation of rental equipment										80,391	73,139	69,908
Gross profit		70,997	78,282	59,881	57,005	65,103	64,050	53,928	50,170	266,165	233,251	206,345
Selling and administrative expenses										124,793	115,770	111,605
Income from operations		38,248	46,748	29,066	27,310	35,166	35,824	24,449	22,042	141,372	117,481	94,740
Interest expense (income) allocation										12,331	(12,297)	(11,622)
Income before provision for income taxes		35,454	43,455	25,965	24,251	32,018	32,553	21,106	19,018	129,125	104,695	83,452
Rental equipment acquisitions										170,018	134,098	98,107
Accounts receivable, net (period end)		128,099				121,016				128,099	121,016	105,872
Rental equipment, at cost (period end)		1,520,411				1,416,000				1,520,411	1,416,000	1,347,533
Rental equipment, net book value (period end)		967,500	$ 958,610	$ 943,152	$ 912,878	901,015	$ 888,607	$ 876,522	$ 865,338	967,500	901,015	862,320
Mobile Modular [Member]
Segment Reporting Information [Line Items]
Rental revenues										182,316	159,136	142,584
Rental related services revenues										69,395	54,696	50,448
Sales and other revenues										49,299	40,742	38,234
Total revenues										301,010	254,574	231,266
Depreciation of rental equipment										22,071	21,200	21,247
Gross profit										143,618	120,750	103,935
Selling and administrative expenses										65,699	58,017	55,583
Income from operations										77,919	62,733	48,352
Interest expense (income) allocation										7,946	(7,132)	(6,671)
Income before provision for income taxes										69,973	55,601	41,681
Rental equipment acquisitions										75,433	63,374	34,526
Accounts receivable, net (period end)		83,182				72,295				83,182	72,295	59,274
Rental equipment, at cost (period end)		868,807				817,375				868,807	817,375	775,400
Rental equipment, net book value (period end)		610,048				572,032				$ 610,048	$ 572,032	$ 543,857
Utilization (period end)	[1]									79.10%	79.30%	77.80%
Average utilization	[1]									79.20%	78.20%	76.80%
TRS-RenTelco [Member]
Segment Reporting Information [Line Items]
Rental revenues										$ 103,704	$ 89,937	$ 82,812
Rental related services revenues										3,260	3,300	2,858
Sales and other revenues										24,519	25,420	22,374
Total revenues										131,483	118,657	108,044
Depreciation of rental equipment										41,948	36,011	32,891
Gross profit										60,748	54,773	50,289
Selling and administrative expenses										24,645	22,823	22,171
Income from operations										36,103	31,950	28,118
Interest expense (income) allocation										1,970	(2,696)	(2,320)
Income before provision for income taxes										34,217	28,765	26,132
Rental equipment acquisitions										89,759	65,467	58,781
Accounts receivable, net (period end)		23,788				20,732				23,788	20,732	19,581
Rental equipment, at cost (period end)		335,343				285,052				335,343	285,052	262,325
Rental equipment, net book value (period end)		172,413				131,450				$ 172,413	$ 131,450	$ 109,482
Utilization (period end)	[1]									64.50%	62.10%	61.70%
Average utilization	[1]									66.20%	62.70%	62.90%
Adler Tanks [Member]
Segment Reporting Information [Line Items]
Rental revenues										$ 67,869	$ 69,701	$ 64,021
Rental related services revenues										28,383	24,911	24,762
Sales and other revenues										1,671	1,441	2,572
Total revenues										97,923	96,053	91,355
Depreciation of rental equipment										16,372	15,928	15,770
Gross profit										47,014	48,055	43,218
Selling and administrative expenses										29,321	30,026	29,542
Income from operations										17,693	18,029	13,676
Interest expense (income) allocation										3,436	(3,252)	(3,071)
Income before provision for income taxes										14,257	14,777	10,605
Rental equipment acquisitions										4,826	5,257	4,800
Accounts receivable, net (period end)		17,281				19,992				17,281	19,992	18,663
Rental equipment, at cost (period end)		316,261				313,573				316,261	313,573	309,808
Rental equipment, net book value (period end)		185,039				197,533				$ 185,039	$ 197,533	$ 208,981
Utilization (period end)	[1]									48.40%	56.40%	57.50%
Average utilization	[1]									54.70%	59.90%	56.00%
Enviroplex [Member]
Segment Reporting Information [Line Items]
Sales and other revenues	[2]									$ 39,814	$ 29,046	$ 31,369
Total revenues	[2]									39,814	29,046	31,369
Gross profit	[2]									14,785	9,673	8,903
Selling and administrative expenses	[2]									5,128	4,904	4,309
Income from operations	[2]									9,657	4,769	4,594
Interest expense (income) allocation	[2]									(1,021)	783	440
Income before provision for income taxes	[2]									10,678	5,552	5,034
Accounts receivable, net (period end)	[2]	$ 3,848				$ 7,997				$ 3,848	$ 7,997	$ 8,354

[1] Utilization is calculated each month by dividing the cost of rental equipment on rent by the total cost of rental equipment excluding new equipment inventory and accessory equipment.  The average utilization for the period is calculated using the average costs of rental equipment.

[2] Gross Enviroplex sales revenues were $39,814, $30,407 and $31,369 in 2019, 2018 and 2017, respectively.  There were $1,361 inter-segment sales to Mobile Modular in 2018, which have been eliminated in consolidation.  There were no inter-segment sales in 2019 and 2017.