Segment Reporting - Summarized Financial Information for Company's Reportable Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Rental revenues	$ 65,502mgrc_Rental	$ 62,430mgrc_Rental
Rental related services revenues	15,367mgrc_RentalRelatedServices	13,512mgrc_RentalRelatedServices
Sales and other revenues	9,319mgrc_SalesAndOtherRevenueNet	11,618mgrc_SalesAndOtherRevenueNet
Total revenues	90,188us-gaap_Revenues	87,560us-gaap_Revenues
Depreciation of rental equipment	18,682	17,897
Gross profit	39,087us-gaap_GrossProfit	38,638us-gaap_GrossProfit
Selling and administrative expenses	25,212	23,411
Income (loss) from operations	13,875us-gaap_OperatingIncomeLoss	15,227us-gaap_OperatingIncomeLoss
Interest expense (income) allocation	2,391us-gaap_InterestIncomeExpenseNet	2,203us-gaap_InterestIncomeExpenseNet
Income (loss) before provision for income taxes	11,316	12,936
Rental equipment acquisitions	35,254	30,395
Accounts receivable, net (period end)	89,361us-gaap_AccountsReceivableNet	83,071us-gaap_AccountsReceivableNet	101,294us-gaap_AccountsReceivableNet
Rental equipment, at cost (period end)	1,254,316	1,159,802	1,229,638
Rental equipment, net book value (period end)	839,078	775,875	825,750
Enviroplex [Member]
Segment Reporting Information [Line Items]
Sales and other revenues	312	1,105
Total revenues	312	1,105
Gross profit	66	419
Selling and administrative expenses	820	738
Income (loss) from operations	(754)	(319)
Interest expense (income) allocation	(48)	(46)
Income (loss) before provision for income taxes	(706)	(273)
Accounts receivable, net (period end)	2,132	1,398
Mobile Modular [Member]
Segment Reporting Information [Line Items]
Rental revenues	26,408	21,533
Rental related services revenues	9,103	7,317
Sales and other revenues	3,373	4,790
Total revenues	38,884	33,640
Depreciation of rental equipment	4,561	3,831
Gross profit	15,704	12,704
Selling and administrative expenses	11,356	9,740
Income (loss) from operations	4,348	2,964
Interest expense (income) allocation	1,253	1,103
Income (loss) before provision for income taxes	3,095	1,861
Rental equipment acquisitions	16,359	16,825
Accounts receivable, net (period end)	45,818	36,512
Rental equipment, at cost (period end)	678,990	607,616
Rental equipment, net book value (period end)	484,598	426,983
Utilization (period end)	74.50%	69.40%
Average utilization	74.20%	69.90%
TRS-RenTelco [Member]
Segment Reporting Information [Line Items]
Rental revenues	22,111	23,760
Rental related services revenues	656	722
Sales and other revenues	5,327	5,159
Total revenues	28,094	29,641
Depreciation of rental equipment	10,152	10,391
Gross profit	11,310	13,075
Selling and administrative expenses	6,118	6,037
Income (loss) from operations	5,192	7,038
Interest expense (income) allocation	529	523
Income (loss) before provision for income taxes	4,495	6,427
Rental equipment acquisitions	16,230	8,375
Accounts receivable, net (period end)	23,095	23,731
Rental equipment, at cost (period end)	269,575	263,545
Rental equipment, net book value (period end)	109,887	106,164
Utilization (period end)	58.60%	56.40%
Average utilization	59.90%	56.80%
Adler Tanks [Member]
Segment Reporting Information [Line Items]
Rental revenues	16,983	17,137
Rental related services revenues	5,608	5,473
Sales and other revenues	307	564
Total revenues	22,898	23,174
Depreciation of rental equipment	3,969	3,675
Gross profit	12,007	12,440
Selling and administrative expenses	6,918	6,896
Income (loss) from operations	5,089	5,544
Interest expense (income) allocation	657	623
Income (loss) before provision for income taxes	4,432	4,921
Rental equipment acquisitions	2,665	5,195
Accounts receivable, net (period end)	18,316	21,430
Rental equipment, at cost (period end)	305,751	288,641
Rental equipment, net book value (period end)	$ 244,593	$ 242,728
Utilization (period end)	61.10%	64.50%
Average utilization	61.10%	61.00%

Depreciation of rental equipment.

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- Definition

Average utilization.

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No definition available.

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- Definition

Rate of utilization is 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.

+ References

No definition available.

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- Definition

Rental equipment acquired to be used in the leasing operations.

+ References

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- Definition

Rental revenues.

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No definition available.

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- Definition

Rental related services revenues.

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No definition available.

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- Definition

Aggregate revenue during the period from sale of goods and services in the normal course of business, after deducting returns, allowances and discounts.

+ References

No definition available.

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- Definition

For an unclassified balance sheet, the amount due from customers or clients for goods or services that have been delivered or sold in the normal course of business, reduced to their estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 3

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-Topic 942

-SubTopic 210

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Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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- Definition

Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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-Publisher FASB

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-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h)(1)(i))

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- Definition

The net amount of operating interest income (expense).

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-Topic 942

-SubTopic 225

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-Subparagraph (SX 210.9-04.10)

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The net result for the period of deducting operating expenses from operating revenues.

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- Definition

Amount before accumulated depreciation of physical assets used in the normal conduct of business to produce goods and services subject to or available for lease.

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- Definition

The amount of property, by major property class, net of accumulated depreciation, subject to or available for lease as of the balance sheet date.

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- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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- Definition

The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

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-Number 210

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