Credit Facilities and Mortgage Notes Payable - Outstanding Debt Excluding Capital Leases (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Outstanding debt	$ 345,339	$ 487,791
Unsecured Credit Facility [Member]
Debt Instrument [Line Items]
Outstanding debt	256,500
Secured Credit Facility [Member]
Debt Instrument [Line Items]
Outstanding debt		316,500
Richmond Credit Facility [Member]
Debt Instrument [Line Items]
Outstanding debt	70,000	70,000
Atlanta-Metro Equipment Loan [Member]
Debt Instrument [Line Items]
Outstanding debt	18,839	20,931
Miami Loan [Member]
Debt Instrument [Line Items]
Outstanding debt		26,048
Atlanta-Suwanee Land Loan [Member]
Debt Instrument [Line Items]
Outstanding debt		1,600
Lenexa Loan [Member]
Debt Instrument [Line Items]
Outstanding debt		2,712
Santa Clara Bridge Loan [Member]
Debt Instrument [Line Items]
Outstanding debt		$ 50,000