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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.19)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

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-Name Accounting Standards Codification

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-SubTopic 10

-Section 50

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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

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-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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Stockholders' Equity and Noncontrolling Interests - Additional Information (Detail) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended		0 Months Ended		1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Feb. 12, 2013	Nov. 12, 2014	Dec. 31, 2014
Class of Stock [Line Items]
Income attributable to noncontrolling interests	$ 2,474,000	$ 2,424,000
6.875 Series C Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Number of depositary shares sold			5.6
Depository shares to cumulative redeemable preferred stock ratio			1.00%
Percentage of redeemable preferred stock			6.875%
Cash proceeds from sale depositary shares			135,200,000
Dividend payment accrual date			Feb. 12, 2018
Cumulative redeemable preferred stock liquidation preference (in usd per share)			$ 25.00
Annual dividend on depositary shares (in usd per share)			$ 1.71875
Series C Preferred Stock
Class of Stock [Line Items]
Number of depositary shares sold				1.6
Percentage of redeemable preferred stock			6.875%
Cash proceeds from sale depositary shares				$ 39,300,000
Series A Preferred Stock
Class of Stock [Line Items]
Dividend rate on preferred stock					8.00%