Deferred Financing and Leasing Costs (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Amortization of Financing Costs	$ 4,800,000	$ 4,100,000	$ 4,900,000
Amortization of Deferred Leasing Costs and Intangible Leases, Acquired-in-place	51,300,000	39,200,000	24,000,000
Finite-Lived Intangible Assets, Gross [Abstract]
Deferred financing costs, gross	38,445,000	36,883,000
Deferred leasing costs, gross	215,714,000	192,194,000
Intangible - market rent, gross	18,082,000	19,366,000
Intangible - origination value, gross	103,512,000	117,905,000
Finite-Lived Intangible Assets, Gross	375,753,000	366,348,000
Finite-Lived Intangible Assets, Accumulated Amortization [Abstract]
Deferred financing costs, accumulated amortization	(20,284,000)	(17,536,000)
Deferred leasing costs, accumulated amortization	(100,702,000)	(91,989,000)
Intangible - market rent, accumulated amortization	(8,266,000)	(4,180,000)
Intangible - origination value, accumulated amortization	(40,215,000)	(26,576,000)
Finite-Lived Intangible Assets, Accumulated Amortization	(169,467,000)	(140,281,000)
Deferred financing and leasing costs, net	$ 206,286,000	$ 226,067,000