Indebtedness (Schedule Of Indebtedness) (Details) (USD $) In Thousands, unless otherwise specified				12 Months Ended			12 Months Ended				12 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Senior Unsecured Notes [Member]		Dec. 31, 2010 Senior Unsecured Notes [Member]	Dec. 31, 2011 Secured Mortgage Notes [Member]		Dec. 31, 2010 Secured Mortgage Notes [Member]	Oct. 31, 2011 5.125% Senior Unsecured Notes [Member]	Dec. 31, 2011 Senior Unsecured Notes Not Maturing In 2011 [Member]	Dec. 31, 2011 Senior Unsecured Notes Mature In 2012 [Member]	Dec. 31, 2011 Unsecured Lines Of Credit [Member]		Dec. 31, 2010 Unsecured Lines Of Credit [Member]
Debt Instrument [Line Items]
Unsecured debt				$ 375,775		$ 385,412						$ 95,684	$ 135,000
Secured debt							459,668		647,837
Total long-term debt	$ 970,443	$ 1,033,249
Payment Terms				Int.			Prin. and Int.						N/A
Interest Rate, Minimum				4.75%	[1]		4.88%
Interest Rate, Maximum				6.30%	[1]		5.99%
Interest rate, stated percentage										5.125%
Interest rate, spread over LIBOR													2.30%	[2]
Debt instrument, Maturity													2014	[2]
Debt instrument, Maturity Date Range, Start				2012	[1]		2013	[3]			2013
Debt instrument, Maturity Date Range, End				2017	[1]		2019	[3]			2019
Remaining maturity period, start				2013
Remaining maturity period, end				2017
weighted average interest rate	6.00%	6.30%	6.30%										2.60%

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

[2] Represents stated rate. At December 31, 2011, the weighted average interest rate was 2.60%. See discussion below relating to the refinancing of the lines of credit in January 2012, at which time the stated rate was reduced to the London Interbank Offered Rate ("LIBOR") + 1.40%.

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