Financing Activity - Additional Information (Detail) (USD $)	9 Months Ended			3 Months Ended	9 Months Ended	0 Months Ended	3 Months Ended	9 Months Ended	0 Months Ended		9 Months Ended			1 Months Ended	3 Months Ended		9 Months Ended								1 Months Ended	9 Months Ended		3 Months Ended	1 Months Ended	9 Months Ended						0 Months Ended					9 Months Ended
	Sep. 30, 2014 Extension	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2013 2010 Term Loan [Member]	Sep. 30, 2013 2010 Term Loan [Member]	Jan. 08, 2014 Two Thousand Fourteen Term Loans [Member]	Sep. 30, 2014 Two Thousand Fourteen Term Loans [Member]	Sep. 30, 2014 Two Thousand Fourteen Term Loans [Member]	Jan. 08, 2014 Two Thousand Fourteen Term Loans [Member] Minimum [Member]	Jan. 08, 2014 Two Thousand Fourteen Term Loans [Member] Maximum [Member]	Sep. 30, 2014 Two Thousand Fourteen Term Loans and Two Thousand Thirteen Revolving Facility [Member]	Sep. 30, 2014 Two Thousand Fourteen Term Loans and Two Thousand Thirteen Revolving Facility [Member] Minimum [Member]	Sep. 30, 2014 Two Thousand Fourteen Term Loans and Two Thousand Thirteen Revolving Facility [Member] Maximum [Member]	Jul. 31, 2014 2013 Revolving Credit Facility [Member]	Sep. 30, 2014 2013 Revolving Credit Facility [Member]	Sep. 30, 2013 2013 Revolving Credit Facility [Member]	Sep. 30, 2014 2013 Revolving Credit Facility [Member]	Sep. 30, 2013 2013 Revolving Credit Facility [Member]	Sep. 30, 2014 2013 Revolving Credit Facility [Member] Minimum [Member]	Sep. 30, 2014 2013 Revolving Credit Facility [Member] Minimum [Member] LIBOR [Member]	Sep. 30, 2014 2013 Revolving Credit Facility [Member] Maximum [Member]	Sep. 30, 2014 2013 Revolving Credit Facility [Member] Maximum [Member] LIBOR [Member]	Sep. 30, 2014 2013 Revolving Credit Facility [Member] First Extension [Member]	Sep. 30, 2014 2013 Revolving Credit Facility [Member] Second Extension [Member]	Apr. 30, 2013 2010 Credit Facility [Member]	Sep. 30, 2013 2010 Credit Facility [Member]	Apr. 16, 2013 2010 Credit Facility [Member]	Sep. 30, 2013 Revolving Credit Facility [Member]	Apr. 30, 2013 2010 Term Loan [Member]	Sep. 30, 2013 2010 Term Loan [Member]	Apr. 16, 2013 2010 Term Loan [Member]	Sep. 30, 2014 Five Year Term Loan [Member]	Sep. 30, 2014 Seven Year Term Loan [Member]	Sep. 30, 2014 Wells Fargo Bank , NA [Member] 2013 Revolving Credit Facility [Member]	Apr. 17, 2013 Wells Fargo Bank , NA [Member] 2013 Revolving Credit Facility [Member]	Jan. 08, 2014 Wells Fargo Bank, NA and Capital One, NA [Member] Seven Year Term Loan [Member]	Jan. 08, 2014 Wells Fargo Bank, NA and US Bank N [Member] Five Year Term Loan [Member]	Jan. 08, 2014 London Interbank Offered Rate (LIBOR) [Member] Wells Fargo Bank, NA and Capital One, NA [Member] Seven Year Term Loan [Member]	Jan. 08, 2014 London Interbank Offered Rate (LIBOR) [Member] Wells Fargo Bank, NA and US Bank N [Member] Five Year Term Loan [Member]	Sep. 30, 2014 Springfield Town Center [Member]	Sep. 30, 2014 Ratio One [Member] London Interbank Offered Rate (LIBOR) [Member] Wells Fargo Bank , NA [Member] Revolving Credit Facility [Member]	Sep. 30, 2014 Ratio One [Member] London Interbank Offered Rate (LIBOR) [Member] Wells Fargo Bank, NA and Capital One, NA [Member] Seven Year Term Loan [Member]	Sep. 30, 2014 Ratio One [Member] London Interbank Offered Rate (LIBOR) [Member] Wells Fargo Bank, NA and US Bank N [Member] Five Year Term Loan [Member]
Debt Instrument [Line Items]
Revolving Facility Debt Used to Repay Mortgage Debt														$ 50,000,000
Unsecured Debt																																100,000,000	30,000,000
Debt Instrument, Face Amount						250,000,000																														100,000,000	150,000,000.0
Debt Instrument, Term																																				7 years	5 years
Senior Unsecured Credit Facility																																		400,000,000	400,000,000.0
Amount outstanding			130,000,000												0		0														97,500,000
Unused portion of line of credit															392,900,000		392,900,000
Interest expense excluding non-cash amortization of finance costs					2,400,000		1,200,000	3,400,000							400,000	800,000	1,200,000	1,600,000								400,000
Non-cash amortization of deferred financing fees							100,000	200,000							400,000	400,000	1,100,000	800,000								800,000
Line of Credit Facility, Deferred Draw Period, Maximum						1 year
Revolving Credit Facility Extension Options Available	2
Outstanding commitments																							0.15%	0.20%
Weighted average interest rate of Term Loan				3.93%																1.50%		2.05%
Stated Interest Rate															1.70%		1.70%
Capitalization Rate									6.50%	7.50%									6.50%		7.50%
Debt Instrument, Basis Spread on Variable Rate																																						1.95%	1.45%		1.50%	1.80%	1.35%
Sales Per Square Foot						500											500
Percentage of unused portion of the 2013 Revolving Facility																	0.30%																			0.35%	0.20%
Maximum amount available under revolving facility through accordion option																																		600,000,000		200,000,000	300,000,000
Line of Credit Facility, Accordion Option, Minimum Incremental Increase															5,000,000		5,000,000																			5,000,000	5,000,000
Line of Credit Facility, Accordion Option, Minimum Increase															25,000,000		25,000,000																			25,000,000	25,000,000
Minimum tangible net worth											75.00%
Net proceeds of equity issuances											75.00%
Maximum secured indebtedness												0.60	0.625
Maximum Investments in Persons other than Subsidiaries, Consolidated Affiliates and Unconsolidated Affiliates											5.00%
Maximum Mortgages in Favor of the Borrower or any other Subsidiary											5.00%
Maximum Aggregate Value of Investments to Gross Asset Value											10.00%
Maximum Investments in Consolidation Exempt Entities to Gross Asset Value											25.00%
Maximum Projects Under Development to Gross Asset Value											15.00%
Aggregate of Consolidation Exempt Entities and Projects to Gross Asset Value											35.00%
Minimum ratio of Adjusted EBITDA to Fixed Charges													1.50
Unencumbered Debt Yield											12.00%
Investment Percentage of Gross Asset Value											1.75
Maximum Ratio of Secured Indebtedness to Gross Asset Value											0.60
Investment Percentage of Gross Asset Value						2.50%
Percentage of distribution related to FFO											95.00%
REIT Taxable Income distributions											110.00%
Line of Credit Facility, Maximum Borrowing Capacity																											250,000,000.0									100,000,000.0	150,000,000.0
Repayment of outstanding amount under revolving facility	(130,000,000)	182,000,000
Debt Instrument, Number of Loan Entered During Period						2
Accelerated amortization of deferred financing fees																									100,000	900,000				800,000
Permanent repayments of 2010 Term Loan																												84,500,000	97,500,000
Minimum Percentage of Total Guarantors Required to be Guarantors Based on Gross Asset Value											95.00%
Maximum Unsecured Borrowing Amount Under Unencumbered Debt Yield Covenant											561,400,000
Letters of Credit Outstanding, Amount															$ 7,100,000		$ 7,100,000																							$ 46,500,000
Letter of Credit, Initial Fee in Effect																																								1.15%
Line of Credit Facility, Prepayment Penalty, Next Twelve Months																																				3.00%
Line of Credit Facility, Prepayment Penalty, Year Two																																				2.00%
Line of Credit Facility, Prepayment Penalty, Year Three																																				1.00%
Debt Instrument, Interest Rate at Period End																																1.60%	2.10%