Indebtedness (Schedule Of Indebtedness) (Detail) (USD $) In Thousands, unless otherwise specified	1 Months Ended	9 Months Ended
	Oct. 31, 2012	Sep. 30, 2012		Dec. 31, 2011
Debt Instrument [Line Items]
Total		$ 1,036,492		$ 970,443
Senior Notes [Member]
Debt Instrument [Line Items]
Senior Unsecured Notes		280,091		375,775
Interest Rate, minimum		4.75%
Interest Rate, maximum		6.30%
Payment Terms		Int.
Senior Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, Maturity Date		2013	[1]
Senior Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, Maturity Date		2017	[1]
Unsecured Bank Term Loan [Member]
Debt Instrument [Line Items]
Senior Unsecured Notes		300,000
Interest Rate, spread over LIBOR		1.90%	[2]
Payment Terms		Int.
Debt instrument, Maturity Date		2018
Weighted average interest rate	3.24%	3.44%
Reduction in stated interest rate		LIBOR plus 1.70
Lines of Credit [Member]
Debt Instrument [Line Items]
Senior Unsecured Notes				135,000
Interest Rate, spread over LIBOR	1.225%	1.40%	[3]
Payment Terms		Int.
Debt instrument, Maturity Date		2016
Weighted average interest rate		0.00%
Secured Mortgage Notes [Member]
Debt Instrument [Line Items]
Secured Mortgage Notes		456,401		459,668
Interest Rate, minimum		4.88%
Interest Rate, maximum		5.99%
Payment Terms		Prin. and Int.
Secured Mortgage Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, Maturity Date		2013	[4]
Secured Mortgage Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, Maturity Date		2019	[4]
Senior Unsecured Notes Maturing In 2013 [Member]
Debt Instrument [Line Items]
Senior Unsecured Notes		$ 130,091
Senior Unsecured Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, Maturity Date		2013
Senior Unsecured Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, Maturity Date		2017

[1] There are no remaining maturities of senior unsecured notes in 2012. Senior unsecured notes totaling approximately $130,091 mature in June 2013. The remaining unsecured notes mature in 2017.

[2] Represents stated rate at September 30, 2012. As discussed below and effective October 1, 2012, the stated interest rate was reduced to LIBOR plus 1.70%. As also discussed below, the Company has entered into interest rate swap arrangements that effectively fix the interest rate under this facility. At September 30, 2012, the effective blended interest rate under the Term Loan was 3.44%. Effective October 1, 2012, the effective blended interest rate was reduced to 3.24%.

[3] Represents stated rate at September 30, 2012. As discussed below and effective October 1, 2012, the stated rate was reduced to LIBOR plus 1.225%.

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