Indebtedness (Schedule Of Indebtedness) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Dec. 31, 2011
Debt Instrument [Line Items]
Long-term Debt	$ 939,263		$ 970,443
Mortgage notes not maturing dates, (in year)	2012
Senior Unsecured Notes [Member]
Debt Instrument [Line Items]
Unsecured debt	375,775		375,775
Payment Terms	Int.
Interest Rate, minimum	4.75%
Interest Rate, maximum	6.30%
Debt instrument, Maturity Date range, start	2012	[1]
Debt instrument, Maturity Date range, end	2017	[1]
Unsecured Bank Term Loan [Member]
Debt Instrument [Line Items]
Unsecured debt	100,000
Payment Terms	Int.
Interest Rate, spread over LIBOR	1.90%	[2]
Debt instrument, maturity	2018
Weighted average interest rate	3.45%
Debt instrument, Maturity Date	Jan. 01, 2018
Unsecured Revolving Lines Of Credit [Member]
Debt Instrument [Line Items]
Unsecured debt	4,923		135,000
Payment Terms	Int.
Interest Rate, spread over LIBOR	1.40%	[3]
Debt instrument, maturity	2016
Weighted average interest rate	1.64%
Secured Mortgage Notes [Member]
Debt Instrument [Line Items]
Secured debt	458,565		459,668
Payment Terms	Prin. and Int.
Interest Rate, minimum	4.88%
Interest Rate, maximum	5.99%
Debt instrument, Maturity Date range, start	2013	[4]
Debt instrument, Maturity Date range, end	2019	[4]
Senior Unsecured Notes Maturing In 2012 [Member]
Debt Instrument [Line Items]
Unsecured debt	$ 95,684
Senior Unsecured Notes Not Maturing In 2012 [Member]
Debt Instrument [Line Items]
Debt instrument, Maturity Date range, start	2013
Debt instrument, Maturity Date range, end	2017

[1] Senior unsecured notes totaling approximately $95,684 mature in 2012. The remaining unsecured notes mature between 2013 and 2017.

[2] Represents stated rate. As discussed below, the Company has entered into interest rate swap arrangements that effectively fix the interest rate under this facility at 3.45% as of March 31, 2012.

[3] Represents stated rate. At March 31, 2012, the weighted average interest rate was 1.64%.

[4] There are no maturities of secured notes in 2012. These notes mature between 2013 and 2019.