Subsequent Events (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	1 Months Ended
	Sep. 30, 2012	Oct. 31, 2012 5.5% Mortgage Notes Payable [Member] Subsequent Event [Member]	Nov. 07, 2012 3.375% Unsecured Debt [Member] Subsequent Event [Member]	Dec. 03, 2012 6.30% Unsecured Debt [Member] Subsequent Event [Member] Future Estimate [Member]
Subsequent Event [Line Items]
Secured mortgage indebtedness repaid		$ 53,027
Stated interest rate on notes payable		5.50%	3.375%	6.30%
Maturity date		January 2013	2022
Senior unsecured notes, issued			250,000	130,091
Expected debt extinguishment loss	$ 301			$ 4,100