Consolidated Statements Of Equity (USD $) In Thousands, except Share data, unless otherwise specified	Common Stock [Member]	Additional Paid-In Capital [Member]	Distributions In Excess Of Accumulated Earnings [Member]	Noncontrolling Interest [Member]	Total
Beginning Balance at Dec. 31, 2008	$ 324	$ 857,415	$ (206,961)	$ 260,754	$ 911,532
Beginning Balance, shares at Dec. 31, 2008	32,431,304
Comprehensive income:
Net income			34,419	12,659	47,078
Issuance of common stock, net	12	46,636			46,648
Issuance of common stock, net, shares	1,228,070
Stock-based compensation		7,291			7,291
Stock-based compensation, shares	6,746
Repurchase of common stock		(2,935)			(2,935)
Repurchase of common stock, shares	(97,304)
Conversion of UPREIT Units for common stock	11	21,321		(21,332)	0
Conversion of UPREIT Units for common stock, shares	1,086,612				1,086,612
Adjustment of noncontrolling interest		(7,650)		7,650	0
Dividends and distributions paid			(88,771)	(32,769)	(121,540)
Ending Balance at Dec. 31, 2009	347	922,078	(261,313)	226,962	888,074
Ending Balance, shares at Dec. 31, 2009	34,655,428
Comprehensive income:
Net income			20,081	6,237	26,318
Issuance of common stock, net	28	123,728			123,756
Issuance of common stock, net, shares	2,827,856
Stock-based compensation		7,647			7,647
Stock-based compensation, shares	6,206
Repurchase of common stock	(1)	(3,273)			(3,274)
Repurchase of common stock, shares	(68,265)
Conversion of UPREIT Units for common stock	5	10,229		(10,234)	0
Conversion of UPREIT Units for common stock, shares	528,004				528,004
Issuance of UPREIT Units associated with property acquisition				4,845	4,845
Adjustment of noncontrolling interest		(13,084)		13,084	0
Dividends and distributions paid			(85,579)	(26,653)	(112,232)
Ending Balance at Dec. 31, 2010	379	1,047,325	(326,811)	214,241	935,134
Ending Balance, shares at Dec. 31, 2010	37,949,229				0
Comprehensive income:
Net income			37,856	9,808	47,664
Issuance of common stock, net	39	216,564			216,603
Issuance of common stock, net, shares	3,881,833
Issuance of common stock through public offering, net	60	336,700			336,760
Issuance of common stock through public offering, net, shares	6,000,000
Stock-based compensation		10,105			10,105
Stock-based compensation, shares	21,457
Repurchase of common stock	(1)	(5,769)			(5,770)
Repurchase of common stock, shares	(96,723)
Conversion of UPREIT Units for common stock	6	11,393		(11,399)	0
Conversion of UPREIT Units for common stock, shares	565,509				565,509
Adjustment of noncontrolling interest		(70,755)		70,755	0
Dividends and distributions paid			(103,423)	(27,429)	(130,852)
Ending Balance at Dec. 31, 2011	$ 483	$ 1,545,563	$ (392,378)	$ 255,976	$ 1,409,644
Ending Balance, shares at Dec. 31, 2011	48,321,305