Equity And Noncontrolling Interests (Narrative) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended
	Dec. 31, 2010	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Equity And Noncontrolling Interests [Line Items]
Common stock, shares authorized		100,000,000		100,000,000
Proceeds from sales of common stock		$ 13,982	$ 15,500
Stock repurchase program, authorized amount	200,000
Redemption of preferred stock			49,633
Redemption value of noncontrolling interest in Operating Partnership		7,086		6,840
Noncontrolling interests in the Operating Partnership, net book value		2,925		2,935
At-The-Market Common Equity Sales Program [Member]
Equity And Noncontrolling Interests [Line Items]
Common stock, shares authorized		4,000,000
Common stock, shares issued		317,000	421,000
Proceeds from sales of common stock		13,982	15,500
Shares reserved for issuance		233,000
7 5/8% Series B Preferred Stock [Member]
Equity And Noncontrolling Interests [Line Items]
Redemption of preferred stock			$ 49,571