Consolidated Statements of Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total		Total Stockholders' Equity	Preferred Stock [Member]	Common Stock [Member]	Common Stock Additional Paid-in Capital	Common Stock Distributions in Excess of Earnings	Noncontrolling Interests - Common Units of the Operating Partnership	Series E and Series F Cumulative Redeemable Preferred Stock [Member] Common Stock Distributions in Excess of Earnings	Series A Preferred Units [Member]	Series A Preferred Units [Member] Total Stockholders' Equity	Series A Preferred Units [Member] Common Stock Distributions in Excess of Earnings
Beginning Balance at Dec. 31, 2009	$ 883,838		$ 854,948	$ 121,582	$ 431	$ 913,657	$ (180,722)	$ 28,890
Beginning Balance, shares at Dec. 31, 2009					43,148,762
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	19,886		19,708				19,708	178
Issuance of common stock (Note 10)	299,847		299,847		92	299,755
Issuance of share-based compensation awards (Note 12)	2,151		2,151			2,151
Issuance of share-based compensation awards, shares (Note 12)					3,239
Noncash amortization of share-based compensation	6,687		6,687			6,687
Exercise of stock options, shares					4,000
Exercise of stock options	83		83			83
Issuance of common units in the Operating Partnership in connection with an operating property acquisition (Note 3)	0
Repurchase of common stock and restricted stock units (Note 12)	(2,121)		(2,121)			(2,121)
Repurchase of common stock and restricted stock units, shares (Note 12)					(59,782)
Settlement of restricted stock units for shares of common stock (Note 12)	(1,296)		(1,296)			(1,296)
Settlement of restricted stock units for shares of common stock, shares (Note 12)					53,451
Allocation to the equity component of cash paid upon repurchase of 3.25% Exchangeable Notes (Note 7)	(2,694)		(2,694)			(2,694)
Adjustment for noncontrolling interest (Note 2)	0		(4,724)			(4,724)		4,724
Preferred dividends and distributions	(15,196)		(15,196)				(15,196)
Dividends declared per common share and common unit ($1.40 per share/ unit for 2010, 2011 and $1.63 per share/unit for 2009)	(73,455)		(71,042)				(71,042)	(2,413)
Ending Balance at Dec. 31, 2010	1,117,730		1,086,351	121,582	523	1,211,498	(247,252)	31,379
Ending Balance, shares at Dec. 31, 2010					52,349,670
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	67,489		66,015				66,015	1,474
Issuance of common stock (Note 10)	233,312		233,312		64	233,248
Issuance of common stock, shares (Note 10)					6,392,805
Issuance of share-based compensation awards (Note 12)	2,739		2,739		1	2,738
Issuance of share-based compensation awards, shares (Note 12)					68,727
Noncash amortization of share-based compensation	5,588		5,588			5,588
Exercise of stock options, shares					15,000
Exercise of stock options	395		395			395
Issuance of common units in the Operating Partnership in connection with an operating property acquisition (Note 3)	0
Repurchase of common stock and restricted stock units (Note 12)	(1,152)		(1,152)			(1,152)
Repurchase of common stock and restricted stock units, shares (Note 12)					(11,485)
Exchange of common units of the Operating Partnership (Note 10)	0		91			91		(91)
Exchange of common units of the Operating Partnership, shares (Note 10)					5,000
Adjustment for noncontrolling interest (Note 2)	0		(3,409)			(3,409)		3,409
Preferred Stock Dividends, Income Statement Impact	15,196		15,196				15,196
Preferred dividends and distributions	(15,196)
Dividends declared per common share and common unit ($1.40 per share/ unit for 2010, 2011 and $1.63 per share/unit for 2009)	(83,423)		(81,017)				(81,017)	(2,406)
Ending Balance at Dec. 31, 2011	1,327,482		1,293,717	121,582	588	1,448,997	(277,450)	33,765
Ending Balance, shares at Dec. 31, 2011	58,819,717	[1]			58,819,717
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	277,101		270,914				270,914	6,187
Proceeds from issuance of preferred stock	192,411		192,411	192,411
Redemption of Series E and Series F Preferred units (Note 11), shares				121,582
Stock redeemed during period, value	(126,500)		(126,500)						(4,918)	(2,062)	(2,062)	(2,062)
Issuance of common stock (Note 10)	672,102		672,102		161	671,941
Issuance of common stock, shares (Note 10)					16,024,618
Issuance of share-based compensation awards (Note 12)	1,291		1,291		0	1,291
Issuance of share-based compensation awards, shares (Note 12)					62,137
Noncash amortization of share-based compensation	8,537		8,537			8,537
Exercise of stock options, shares	5,000				5,000
Exercise of stock options	129		129			129
Issuance of common units in the Operating Partnership in connection with an operating property acquisition (Note 3)	5,604							5,604
Repurchase of common stock and restricted stock units (Note 12)	(877)		(877)			(877)
Repurchase of common stock and restricted stock units, shares (Note 12)					(22,312)
Settlement of restricted stock units for shares of common stock (Note 12)	(784)		(784)			(784)
Settlement of restricted stock units for shares of common stock, shares (Note 12)					27,821
Exchange of common units of the Operating Partnership (Note 10)	0		231			231		(231)
Exchange of common units of the Operating Partnership, shares (Note 10)					10,000
Adjustment for noncontrolling interest (Note 2)	0		(3,460)			(3,460)		3,460
Preferred Stock Dividends, Income Statement Impact	14,108		14,108				14,108
Preferred dividends and distributions	(21,088)
Dividends declared per common share and common unit ($1.40 per share/ unit for 2010, 2011 and $1.63 per share/unit for 2009)	(104,393)		(101,911)				(101,911)	(2,482)
Ending Balance at Dec. 31, 2012	$ 2,235,933		$ 2,189,630	$ 192,411	$ 749	$ 2,126,005	$ (129,535)	$ 46,303
Ending Balance, shares at Dec. 31, 2012	74,926,981	[1]			74,926,981

[1] The amount includes nonvested shares.