Summary Of Redeemable Noncontrolling Interest (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Class of Stock [Line Items]
Beginning balance noncontrolling redeemable Operating Partnership Units			$ 14,466
Redemption of operating partnership units			(7,364)
Redemption value in excess of carrying value			523
Net income attributable to noncontrolling interests	151	27	421	811
Distributions			(458)
Adjustment to redemption value			4,223
Ending balance noncontrolling redeemable Operating Partnership Units	$ 11,811		$ 11,811

Amount of Net Income (Loss) attributable to noncontrolling interest.

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The fair value as of the reporting date of noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. The noncontrolling interest holder's ownership (or holders' ownership) may be in the form of common shares (regardless of class), limited partnership units (regardless of class), non-preferential membership interests, or any other form of common equity regardless of investee entity legal form.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 480

-SubTopic 10

-Section S99

-Paragraph 3A

-Subparagraph 14

-URI http://asc.fasb.org/extlink&oid=14643745&loc=SL6540498-122764

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

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number D-98

-Paragraph 43

-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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 480

-SubTopic 10

-Section S99

-Paragraph 3A

-Subparagraph (12)(c)

-URI http://asc.fasb.org/extlink&oid=14643745&loc=SL6540498-122764

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number D-98

-Paragraph 43

-Subparagraph c

-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 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 480

-SubTopic 10

-Section S99

-Paragraph 3A

-Subparagraph (16)(c)

-URI http://asc.fasb.org/extlink&oid=14643745&loc=SL6540498-122764

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 480

-SubTopic 10

-Section S99

-Paragraph 3A

-Subparagraph 15

-URI http://asc.fasb.org/extlink&oid=14643745&loc=SL6540498-122764

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 27

-Subparagraph c

-Appendix A

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