Acquired In-Place Leases Acqured Lease Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Accumulated Amortization	$ (33,111)	$ (29,009)
Finite-Lived Intangible Liabilities, Accumulated Amortization	57,276	49,199
Finite-Lived Intangible LIabilities, Net	(202,169)	(141,049)
Amortization of below market leases, lessor	10,726	8,551	$ 7,130
Net increase in rental income	4,721	1,825	2,705
Amortization of Below Market Lease, Lessee	781	255	255
Net increase in rental expense	491	120	120
Acquired Lease Assets
Total future amortization expense from acquired above market leases	86,997	58,564
Acquired Lease Liabilities
2018	9,990
2019	9,488
2020	8,494
2021	7,869
2022	7,484
Thereafter	101,568
Total future amortization expense from acquired below market leases	144,893
Above Market Leases
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of above market leases, lessor	(6,005)	(6,726)	(4,425)
Amortization of above market leases, lessee	$ (290)	(135)	$ (135)
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	4 years 8 months
Acquired Finite-Lived Intangible Liabilities, Weighted Average Useful Life	19 years 10 months
Acquired Lease Assets
2018	$ 5,810
2019	3,829
2020	3,182
2021	2,804
2022	2,381
Thereafter	35,880
Total future amortization expense from acquired above market leases	53,886
Above Market Leases, Lessor
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	52,393	45,327
Finite-Lived Intangible Assets, Accumulated Amortization	(31,406)	(28,085)
Below Market Leases, Lessee
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	34,604	13,237
Finite-Lived Intangible Assets, Accumulated Amortization	$ (1,705)	(924)
Below Market Lease
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	41 years 7 months
Acquired Finite-Lived Intangible Liabilities, Weighted Average Useful Life	16 years 11 months
Below Market Leases, Lessor
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Liabilities, Gross	$ (193,085)	(138,253)
Finite-Lived Intangible Liabilities, Accumulated Amortization	56,716	48,928
Above Market Leases, Lessee
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Liabilities, Gross	(9,084)	(2,796)
Finite-Lived Intangible Liabilities, Accumulated Amortization	$ 560	$ 271