Summary Of The Debt Obligation And Interest Rate Derivatives (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Line of credit	$ 26,000	$ 46,000
Term notes	575,000	575,000
Mortgage note , total	4,295	4,423
Interest rate derivatives - liability	16,493	10,748
Line Of Credit - Variable Rate LIBOR + 2.0% (2.22% At September30, 2012) [Member]
Debt Instrument [Line Items]
Line of credit	26,000
Debt Instrument, Fair Value	26,000
Payables due 2016	26,000
Term Note - Variable Rate LIBOR+1.50% (2.21% At September30, 2012) [Member]
Debt Instrument [Line Items]
Term notes	20,000
Term note, fair value	20,000
Payables due 2013	20,000
Term Note - Fixed Rate 6.26% [Member]
Debt Instrument [Line Items]
Term notes	80,000
Term note, fair value	82,414
Payables due 2013	80,000
Term Note - Fixed Rate 6.38% [Member]
Debt Instrument [Line Items]
Term notes	150,000
Term note, fair value	164,178
Payables due 2016	150,000
Term Note Variable Interest Rate Libor Plus Two Percent One [Member]
Debt Instrument [Line Items]
Payables due Thereafter	125,000
Term Note Variable Interest Rate Libor Plus Two Percent Two [Member]
Debt Instrument [Line Items]
Payables due Thereafter	100,000
Term Note - Fixed Rate 5.54% [Member]
Debt Instrument [Line Items]
Term notes	100,000
Term note, fair value	97,855
Payables due Thereafter	100,000
Mortgage Note Fixed Interest Rate Six Point Seventy Six Percent [Member]
Debt Instrument [Line Items]
Payables due 2012	8
Payables due 2013	896
Mortgage Note Fixed Interest Rate Six Point Thirty Five Percent [Member]
Debt Instrument [Line Items]
Payables due 2012	8
Payables due 2013	34
Payables due 2014	949
Mortgage Note Fixed Interest Rate Five Point Ninety Nine Percent [Member]
Debt Instrument [Line Items]
Payables due 2012	28
Payables due 2013	119
Payables due 2014	126
Payables due 2015	134
Payables due 2016	142
Payables due Thereafter	1,851
Term note - variable rate LIBOR+2.0% (2.23% At September30, 2012) [Member]
Debt Instrument [Line Items]
Term notes	125,000
Term note, fair value	125,000
Term note - variable rate LIBOR+2.0% (2.22% At September30, 2012) [Member]
Debt Instrument [Line Items]
Term notes	100,000
Term note, fair value	100,000
6.76% Mortgage Note Due September 2013 [Member]
Debt Instrument [Line Items]
Mortgage note , total	904	925
Debt Instrument, Fair Value	936
6.35% Mortgage Note Due March 2014 [Member]
Debt Instrument [Line Items]
Mortgage note , total	991	1,014
Debt Instrument, Fair Value	1,036
5.99% Mortgage Note Due May 2026 [Member]
Debt Instrument [Line Items]
Mortgage note , total	2,400	2,484
Debt Instrument, Fair Value	$ 2,603

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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- Definition

Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 10

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

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- Definition

Amount of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates maturing after the fifth fiscal year following the latest fiscal year.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 47

-Paragraph 10

-Subparagraph b

-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.

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- Definition

Amount of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year.

+ References

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Amount of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates maturing in the fifth fiscal year following the latest fiscal year.

+ References

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- Definition

Amount of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates maturing in the fourth fiscal year following the latest fiscal year.

+ References

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- Definition

Amount of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates maturing in the third fiscal year following the latest fiscal year.

+ References

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- Definition

Amount of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates maturing in the second fiscal year following the latest fiscal year.

+ References

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- Definition

Including the current and noncurrent portions, aggregate carrying amount of all types of notes payable, as of the balance sheet date, with initial maturities beyond one year or beyond the normal operating cycle, if longer.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 13, 16

-Article 9

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

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-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

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-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

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-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 2, 4

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-Paragraph 1

-Subparagraph (SX 210.5-02.19,20,22)

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

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-Publisher FASB

-Name Accounting Standards Codification

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-Name Accounting Standards Codification

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

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