Intangible Assets and Intangible Liabilities - Summary of Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Intangible assets:
Gross amount	$ 506,627		$ 515,889
Accumulated amortization	(252,273)		(245,444)
Intangible assets, Net	254,354		270,445
Intangible liabilities:
Gross amount	181,008		185,191
Accumulated amortization	(91,053)		(89,200)
Intangible Liabilities, Net	89,955		$ 95,991
Leases, Acquired-in-Place, Market Adjustment [Member]
Intangible liabilities:
Amortization of above and below-market leases, net (component of "rental revenue")	3,276	$ 4,420
Leases, Acquired-in-Place [Member]
Intangible liabilities:
Amortization of acquired in-place leases (component of "depreciation and amortization")	$ 13,333	$ 15,293