Intangibles (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Intangible assets and liabilities
Gross intangible lease assets	$ 1,014,460	$ 830,408
Intangible assets, accumulated depreciation and amortization	400,233	349,395
Net intangible lease assets	$ 614,227	$ 481,013
Remaining weighted-average amortization period of intangible assets	14 years	14 years
Below market leases, Gross intangible lease liabilities	$ 204,662	$ 203,374
Above market ground lease, Gross intangible lease liabilities	6,121	6,121
Gross intangible lease liabilities	210,783	209,495
Intangible liabilities, accumulated depreciation and amortization	135,510	124,772
Net intangible lease liabilities	$ 75,273	$ 84,723
Approximate remaining weighted-average amortization period of unfavorable market lease intangibles	9 years	9 years
Additional revenues from the amortization of net below market lease intangibles included in rental income	$ 4,000	$ 3,000	$ 9,000
Additional expense from the amortization of net above market ground lease intangibles included in operating expenses	1,000	1,000	1,000
Additional expense from the amortization of lease-up and non-compete agreement intangibles included in depreciation and amortization expense	76,000	60,000	$ 59,000
Estimated aggregate amortization of Intangible Assets
Estimated aggregate amortization of intangible assets, 2016	97,043
Estimated aggregate amortization of intangible assets, 2017	84,552
Estimated aggregate amortization of intangible assets, 2018	68,999
Estimated aggregate amortization of intangible assets, 2019	55,730
Estimated aggregate amortization of intangible assets, 2020	46,308
Estimated aggregate amortization of intangible assets, thereafter	261,595
Net intangible lease assets	614,227	481,013
Estimate aggregate amortization of Intangible Liabilities
Estimated aggregate amortization of intangible liabilities, 2016	17,545
Estimated aggregate amortization of intangible liabilities, 2017	15,118
Estimated aggregate amortization of intangible liabilities, 2018	12,413
Estimated aggregate amortization of intangible liabilities, 2019	9,758
Estimated aggregate amortization of intangible liabilities, 2020	6,047
Estimated aggregate amortization of intangible liabilities, thereafter	14,392
Net intangible lease liabilities	75,273	84,723
Lease-up intangibles
Intangible assets and liabilities
Gross intangible lease assets	801,513	608,323
Tenant leases | Above market
Intangible assets and liabilities
Gross intangible lease assets	155,048	163,146
Ground leases | Below market
Intangible assets and liabilities
Gross intangible lease assets	$ 57,899	$ 58,939