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

-Publisher FASB

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-Topic 230

-SubTopic 10

-Section 50

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

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The percentage rate used to calculate dividend payments on preferred stock.

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Stockholders' Equity and Noncontrolling Interest - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended			1 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2013	Nov. 30, 2003	Mar. 31, 2008	Nov. 12, 2014	Feb. 12, 2013
Class of Stock [Line Items]
Income attributable to noncontrolling interests	$ 11,045	$ 3,970	$ 6,406
Series A Preferred Stock
Class of Stock [Line Items]
Number of depositary shares sold					4,000,000
Depository shares to cumulative redeemable preferred stock ratio					0.01
Dividend rate on preferred stock					8.00%
Depositary shares, redeemable price (in usd per share)					$ 25.00
Annual dividend on depositary shares					$ 2.00
Cumulative redeemable preferred stock liquidation preference					$ 25.00
Percentage of redeemable preferred stock				60.00%
Series B Preferred Stock
Class of Stock [Line Items]
Number of depositary shares sold						3,173,115
Depository shares to cumulative redeemable preferred stock ratio						0.01
Dividend rate on preferred stock						9.00%
Depositary shares, redeemable price (in usd per share)						$ 25.00
Annual dividend on depositary shares						$ 2.25
Cumulative redeemable preferred stock liquidation preference						$ 25.00
Series B Preferred Stock \| Minimum
Class of Stock [Line Items]
Depository shares redemption date						Mar. 15, 2013
Series C Preferred Stock
Class of Stock [Line Items]
Number of depositary shares sold							1,600,000	5,600,000
Depository shares to cumulative redeemable preferred stock ratio								0.01
Dividend rate on preferred stock								6.875%
Annual dividend on depositary shares								$ 1.71875
Cumulative redeemable preferred stock liquidation preference								$ 25.00
Percentage of redeemable preferred stock								6.875%
Series C preferred stock	$ 39,260	$ 135,221	$ 0				$ 39,260	$ 135,200
Dividends payment date								Apr. 15, 2013
Series C Preferred Stock \| Minimum
Class of Stock [Line Items]
Depository shares redemption date								Feb. 12, 2018
Dividends record date								Feb. 12, 2013
Series C Preferred Stock \| Maximum
Class of Stock [Line Items]
Dividends record date								Mar. 31, 2013