Indebtedness - Information Regarding Indebtedness (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014		Dec. 31, 2013
Debt Instrument [Line Items]
Mortgage Loans Payable, Net	$ 602,927		$ 677,890
Senior Unsecured Notes, Net	364,837		445,916
Unsecured Term Loan	200,000		0
Unsecured Credit Facility	176,000		173,000
Mortgages
Debt Instrument [Line Items]
Mortgage Loans Payable, Net	602,927		677,890
Unamortized Premiums	(96)		(115)
Mortgage Loans Payable, Gross	602,831		677,775
Interest Rate, Minimum	4.03%
Interest Rate, Maximum	8.26%
Effective Interest Rate, Minimum	4.03%
Effective Interest Rate, Maximum	8.26%
Maturity Date Range, Start	Feb. 01, 2016
Maturity Date Range, End	Sep. 01, 2022
Senior Unsecured Notes
Debt Instrument [Line Items]
Senior Unsecured Notes, Net	364,837		445,916
Unamortized Discounts	265		980
Senior Unsecured Notes, Gross	365,102		446,896
Unsecured Term Loan
Debt Instrument [Line Items]
Unsecured Term Loan	200,000	[1]
Interest Rate	1.9045%	[1]
Effective Interest Rate	1.9045%	[1]
Maturity Date	Jan. 29, 2021	[1]
Unsecured Credit Facility
Debt Instrument [Line Items]
Unsecured Credit Facility	176,000	[2]	173,000	[2]
Unsecured Credit Facility, Interest Rate at Period End	1.6561%	[2]
Effective Interest Rate	1.6561%	[2]
Maturity Date	Sep. 29, 2017	[2]
2016 Notes
Debt Instrument [Line Items]
Senior Unsecured Notes, Net	159,607		159,566
Interest Rate	5.75%
Effective Interest Rate	5.91%
Maturity Date	Jan. 15, 2016
2017 Notes
Debt Instrument [Line Items]
Senior Unsecured Notes, Net	54,964		54,960
Interest Rate	7.50%
Effective Interest Rate	7.52%
Maturity Date	Dec. 01, 2017
2027 Notes
Debt Instrument [Line Items]
Senior Unsecured Notes, Net	6,066		6,066
Interest Rate	7.15%
Effective Interest Rate	7.11%
Maturity Date	May 15, 2027
2028 Notes
Debt Instrument [Line Items]
Senior Unsecured Notes, Net	31,884		31,883
Interest Rate	7.60%
Effective Interest Rate	8.13%
Maturity Date	Jul. 15, 2028
2032 Notes
Debt Instrument [Line Items]
Senior Unsecured Notes, Net	10,517		10,514
Interest Rate	7.75%
Effective Interest Rate	7.87%
Maturity Date	Apr. 15, 2032
2014 Notes
Debt Instrument [Line Items]
Senior Unsecured Notes, Net	0		81,149
Maturity Date	Jun. 01, 2014
2017 II Notes
Debt Instrument [Line Items]
Senior Unsecured Notes, Net	$ 101,799		$ 101,778
Interest Rate	5.95%
Effective Interest Rate	6.37%
Maturity Date	May 15, 2017

[1] We entered into interest rate protection agreements, with an aggregate notional value of $200,000, to effectively convert the variable rate to a fixed rate. See Note 10.

[2] The maturity date may be extended an additional year at our election, subject to certain restrictions.