Commitments and Contingencies - Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Commitments And Contingencies [Line Items]
Operating ground lease expense	$ 210,000	$ 162,000	$ 219,000
Letter of credit obligations	4,300,000
Development in Process	209,187,000	248,602,000
Deferred leasing costs, Gross	193,015,000	188,181,000
Maximum [Member]
Commitments And Contingencies [Line Items]
Potential payments for tenant allowances	38,100,000
Construction in Progress [Member]
Commitments And Contingencies [Line Items]
Number of Development Buildings Under Commitment	16
Leasable space of buildings	5,000,000
Anticipated aggregate investment	380,800,000
Development Properties [Member]
Commitments And Contingencies [Line Items]
Deferred leasing costs, Gross	11,100,000
Development Not Yet Commenced [Member]
Commitments And Contingencies [Line Items]
Anticipated aggregate investment	13,100,000
Land Improvements	16,200,000
Land Held for Development [Member]
Commitments And Contingencies [Line Items]
Purchase Commitment, Remaining Minimum Amount Committed	$ 52,800,000