Subsequent Events - Additional Information (Detail) (USD $)	6 Months Ended		12 Months Ended	1 Months Ended
	Jun. 30, 2013 Property	Jun. 30, 2012 Property	Dec. 31, 2012 Property	Aug. 02, 2013 Subsequent Events Property	Jul. 19, 2013 Subsequent Events	Jul. 18, 2013 Subsequent Events
Subsequent Event [Line Items]
Paid off and retired a secured mortgage loan	$ 24,429,000	$ 17,432,000		$ 14,046,000
Depositary shares redeemed	4,000,000			2,000,000
Portion of preferred stock	0.0001					0.0001
Dividend rate per share	7.25%			7.25%
Par value of each depositary share	$ 0.01					$ 0.01
Redemption price per share	$ 25.00					$ 25.00
Payments for repurchase of redeemable preferred stock	100,000,000	0		50,000,000
Line of credit facility, maximum borrowing capacity					625,000
Line of credit facility, increase, additional borrowings				825,000
Line of credit facility, interest rate description				145
Number of certain rating agencies				1
Number of years of extension of line of credit facility at election				1 year
Number of industrial properties sold	12	6	26	3
Proceeds from sale of industrial properties				$ 5,982,000