Indebtedness - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended	6 Months Ended
	May 31, 2014	Jun. 30, 2014	Jun. 30, 2014
Debt Instrument [Line Items]
Prepaid secured mortgage indebtedness	$ 120,000
Indebtedness maturity date			2015-02
Stated rate on the indebtedness		4.88%	4.88%
Net gain (loss) on extinguishment of indebtedness		4,287	4,287
Letters of credit issued		420	420
Coverage's ratio			1.5
Company's ratio			2.0
Unencumbered assets to unsecured debt			1.5
Leverage ratio			60.00%
Total secured debt to total asset value			40.00%
Line of credit facility, covenant terms			The Company's Syndicated Line, Cash Management Line, Term Loan and senior unsecured notes contain customary restrictions, representations, covenants and events of default and require the Company to meet certain financial covenants. Debt service and fixed charge coverage covenants require the Company to maintain
Lines of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity		300,000	300,000
Interest Rate, spread over LIBOR			1.225%
Line of credit facility annual facility fees percentage			0.225%
Line of credit facility, expiration year			January 2016
Interest rate based on credit ratings ranges, minimum			1.00%
Interest rate based on credit ratings ranges, maximum			1.80%
Facility fee rate based on credit ratings range, minimum			0.15%
Facility fee rate based on credit ratings range, maximum			0.40%
Line of credit facility, competitive bid option for short-term funds, percentage			50.00%
Unsecured Bank Term Loan [Member]
Debt Instrument [Line Items]
Interest Rate, spread over LIBOR			1.70%
Line of credit facility, expiration year			January 2018
Interest rate based on credit ratings ranges, maximum			2.30%
Time period extension option			6 months
Term loan facility, borrowing capacity		300,000	300,000
Interest rate based on credit ratings ranges, minimum			1.50%
Six-month extension options		2	2
Unsecured Bank Term Loan [Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Interest rate paid under the Term Loan		1.54%	1.54%
Effective blended interest rate on the Term Loan		3.24%	3.24%
Cash Management Line [Member]
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity		$ 30,000	$ 30,000
Line of credit facility, expiration year			January 2016
Number of extension options			1
Time period extension option			1 year