Acquired Leases Intangibles (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 627,106	$ 175,526
Accumulated amortization	(148,280)	(56,695)
Acquired lease intangible assets, net of amortization	478,826	118,831
Finite LIved Intangible Liabilities	593,951	77,718
Finite-Lived Intangible Liabilities, Accumulated Accretion	(56,550)	(23,538)
Finite-Lived Intangible Assets, Amortization Expense	99,613	14,386	$ 11,442
Acquired lease intangible liability accretion	34,922	6,994	4,155
Off-Market Lease, Unfavorable [Member]
Finite-Lived Intangible Assets [Line Items]
Finite Lived Intangible Liabilities, Gross	588,850	71,996
Acquired lease intangible liability accretion	34,786	6,827	3,940
Above Market Ground Rent Lease [Member]
Finite-Lived Intangible Assets [Line Items]
Finite Lived Intangible Liabilities, Gross	5,101	5,722
Above Market Leases [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired lease intangible liability accretion	136	167	215
In-place leases, net
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	470,315	96,178
Finite-Lived Intangible Assets, Amortization Expense	88,284	11,533	9,141
Above Market Leases [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	64,625	14,684
Finite-Lived Intangible Assets, Amortization Expense	9,443	1,742	1,950
Above-market ground leases, net
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	92,166	64,664
Finite-Lived Intangible Assets, Amortization Expense	1,886	1,111	$ 351
Partnership Interest [Member]
Finite-Lived Intangible Assets [Line Items]
Accumulated amortization	148,546	56,694
Acquired lease intangible assets, net of amortization	478,826	118,831
Off-market Lease, Unfavorable	$ 537,401	$ 54,180