Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	6 Months Ended
Jun. 30, 2011
Significant Accounting Policies [Line Items]
Incentive Plan, awards vesting period (in years)	Three- or four-year
Employee Stock Purchase Plan, percentage of common stock fair value that employees can purchase	85.00%
Employees maximum 401(k) contribution	100.00%
Minimum percentage of taxable income distribution to shareholders to be taxed as a REIT	90.00%
Adjustments for New Accounting Pronouncement
Significant Accounting Policies [Line Items]
Amount of the recorded investment in receivables	$ 2,800,000
Allowance for loan losses associated with receivable	$ 300,000

Employee Stock Purchase Plan, Minimum Percentage of Common Stock Fair Value Defined to Purchase Shares By Eligible Participants

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- Definition

Maximum 401(k) Plan Contribution Rates as a Percentage of Employees Earnings

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- Definition

Minimum Percentage of Taxable Income Distribution to Shareholders

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- Definition

Significant Accounting Policies [Line Items]

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- Definition

The effect of a change in method or methods for calculating the allowance for credit losses on the current period provision.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-URI http://asc.fasb.org/extlink&oid=6965416&loc=SL6953423-111524
-Subparagraph (d)

+ Details

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- Definition

Financing receivables that are current.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=6965416&loc=SL6953401-111524

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- Definition

Description of the period of time over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, which may be expressed in a variety of ways (for example, in years, month and year).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph a
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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