Segment Reporting - Summarized Financial Information for Company's Reportable Segments (Parenthetical) (Detail) - USD ($)		3 Months Ended								12 Months Ended
		Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues		$ 148,980,000	$ 156,448,000	$ 137,673,000	$ 129,453,000	$ 147,221,000	$ 173,562,000	$ 127,439,000	$ 122,008,000	$ 572,554,000	$ 570,230,000	$ 498,330,000
Sales revenues										(128,371,000)	(115,303,000)	(96,649,000)
Sales [Member]
Segment Reporting Information [Line Items]
Sales revenues										(124,604,000)	(110,229,000)	(92,618,000)
Enviroplex [Member]
Segment Reporting Information [Line Items]
Revenues	[1]									32,737,000	39,814,000	29,046,000
Sales revenues	[1]									(32,737,000)	(39,814,000)	(29,046,000)
Mobile Modular [Member]
Segment Reporting Information [Line Items]
Revenues										321,524,000	301,010,000	254,574,000
Sales revenues										(65,278,000)	(49,299,000)	(40,742,000)
Operating Segments [Member] | Enviroplex [Member] | Sales [Member]
Segment Reporting Information [Line Items]
Revenues										34,014,000	39,814,000	30,407,000
Inter-segment Eliminations [Member]
Segment Reporting Information [Line Items]
Sales revenues											$ 0
Type of Revenue [Extensible List]											us-gaap:ProductMember
Inter-segment Eliminations [Member] | Mobile Modular [Member]
Segment Reporting Information [Line Items]
Sales revenues										$ 1,277,000		$ 1,361,000
Type of Revenue [Extensible List]										us-gaap:ProductMember		us-gaap:ProductMember

[1] Gross Enviroplex sales revenues were $34,014, $39,814 and $30,407 in 2020, 2019 and 2018, respectively.  There were $1,277 and $1,361 inter-segment sales to Mobile Modular in 2020 and 2018, which have been eliminated in consolidation.  There were no inter-segment sales in 2019.