Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summarized financial information for the Company's reportable segments
Rental Revenues	$ 65,117	$ 63,418	$ 60,389	$ 59,520	$ 62,798	$ 60,964	$ 57,118	$ 54,026	$ 248,444	$ 234,906	$ 200,615
Rental Related Services Revenues									46,920	39,486	34,702
Sales and Other Revenues									66,444	66,382	54,055
Total Revenues	101,950	99,430	83,765	78,929	85,206	104,961	79,530	72,973	364,074	342,670	291,400
Depreciation of Rental Equipment									63,819	60,187	56,399
Gross Profit	44,039	43,640	40,780	39,835	44,193	47,387	39,359	35,852	168,294	166,791	130,815
Interest Expense (Income) Allocation									9,149	7,606	6,186
Income (Loss) before Provision for Income Taxes	18,851	20,480	17,235	16,301	21,231	25,255	18,760	15,812	72,867	81,058	59,050
Rental Equipment Acquisitions									4,491	8,186	5,388
Accounts Receivable, net (period end)	92,256				92,671				92,256	92,671
Rental Equipment, at cost (period end)	1,072,845				999,189				1,072,845	999,189
Rental Equipment, net book value (period end)	718,853	719,636	710,918	693,577	673,146	655,854	632,518	608,115	718,853	673,146
Mobile Modular [Member]
Summarized financial information for the Company's reportable segments
Rental Revenues									79,518	79,969	82,648
Rental Related Services Revenues									25,775	24,063	22,947
Sales and Other Revenues									14,474	20,577	21,117
Total Revenues									119,767	124,609	126,712
Depreciation of Rental Equipment									13,942	13,780	13,734
Gross Profit									52,022	55,193	56,902
Interest Expense (Income) Allocation									4,547	4,036	3,513
Income (Loss) before Provision for Income Taxes									13,443	19,026	25,080
Rental Equipment Acquisitions									21,042	33,824	22,948
Accounts Receivable, net (period end)	39,066				44,013				39,066	44,013	39,041
Rental Equipment, at cost (period end)	551,101				539,147				551,101	539,147	514,548
Rental Equipment, net book value (period end)	384,813				383,621				384,813	383,621	369,195
Utilization (period end)									66.70%	67.30%	67.20%
Average Utilization									66.40%	67.10%	67.70%
TRS-RenTelco [Member]
Summarized financial information for the Company's reportable segments
Rental Revenues									101,645	95,694	82,540
Rental Related Services Revenues									3,673	3,133	2,240
Sales and Other Revenues									27,855	26,488	22,982
Total Revenues									133,173	125,315	107,762
Depreciation of Rental Equipment									38,174	38,039	37,017
Gross Profit									62,083	57,069	43,475
Interest Expense (Income) Allocation									2,384	2,124	1,791
Income (Loss) before Provision for Income Taxes									33,631	29,024	19,263
Rental Equipment Acquisitions									51,793	55,302	42,406
Accounts Receivable, net (period end)	24,654				24,236				24,654	24,236	20,620
Rental Equipment, at cost (period end)	266,934				258,586				266,934	258,586	250,125
Rental Equipment, net book value (period end)	107,999				105,565				107,999	105,565	98,444
Utilization (period end)									64.10%	67.10%	64.30%
Average Utilization									65.80%	66.00%	66.00%
Adler Tanks [Member]
Summarized financial information for the Company's reportable segments
Rental Revenues									67,281	59,243	35,427
Rental Related Services Revenues									17,472	12,290	9,515
Sales and Other Revenues									2,558	425	289
Total Revenues									87,311	71,958	45,231
Depreciation of Rental Equipment									11,703	8,368	5,648
Gross Profit									51,157	49,619	27,685
Interest Expense (Income) Allocation									2,350	1,659	1,080
Income (Loss) before Provision for Income Taxes									26,706	31,262	14,444
Rental Equipment Acquisitions									55,919	68,628	52,353
Accounts Receivable, net (period end)	24,523				19,226				24,523	19,226	14,751
Rental Equipment, at cost (period end)	254,810				201,456				254,810	201,456	133,095
Rental Equipment, net book value (period end)	226,041				183,960				226,041	183,960	123,941
Utilization (period end)									67.50%	79.80%	84.90%
Average Utilization									71.50%	86.20%	76.00%
Enviroplex [Member]
Summarized financial information for the Company's reportable segments
Rental Revenues
Rental Related Services Revenues
Sales and Other Revenues									23,823	20,788	11,695
Total Revenues									23,823	20,788	11,695
Depreciation of Rental Equipment
Gross Profit									3,032	4,910	2,753
Interest Expense (Income) Allocation									(132)	(213)	(198)
Income (Loss) before Provision for Income Taxes									(913)	1,746	263
Rental Equipment Acquisitions
Accounts Receivable, net (period end)	4,213				5,197				4,213	5,197	2,076
Rental Equipment, at cost (period end)
Rental Equipment, net book value (period end)
Consolidated [Member]
Summarized financial information for the Company's reportable segments
Rental Revenues									248,444	234,906	200,615
Rental Related Services Revenues									46,920	39,486	34,702
Sales and Other Revenues									68,710	68,278	56,083
Total Revenues									364,074	342,670	291,400
Depreciation of Rental Equipment									63,819	60,187	56,399
Gross Profit									168,294	166,791	130,815
Interest Expense (Income) Allocation									9,149	7,606	6,186
Income (Loss) before Provision for Income Taxes									72,867	81,058	59,050
Rental Equipment Acquisitions									128,754	157,754	117,707
Accounts Receivable, net (period end)	92,456				92,671				92,456	92,671	76,488
Rental Equipment, at cost (period end)	1,072,845				999,189				1,072,845	999,189	897,768
Rental Equipment, net book value (period end)	$ 718,853				$ 673,146				$ 718,853	$ 673,146	$ 591,580