Summary of Significant Accounting Policies - Future Amortization of Deferred Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Year Ending December 31,
2019	$ 17,263
2020	22,617
2021	21,710
2022	21,463
2023	20,523
Thereafter	162,132
Total	265,708
Total	(27,873)	$ (27,218)
Credit Facility Financing Costs [Member]
Year Ending December 31,
2019	413
2020	541
2021	28
2022	0
2023	0
Thereafter	0
Total	982
Leasing Costs [Member]
Year Ending December 31,
2019	241
2020	365
2021	346
2022	334
2023	300
Thereafter	1,085
Total	2,671
Lease Intangibles (In-place)
Year Ending December 31,
2019	7,001
2020	8,805
2021	8,295
2022	7,482
2023	6,806
Thereafter	38,401
Total	76,790
Lease Intangibles (Above-Market)
Year Ending December 31,
2019	13,005
2020	17,338
2021	17,150
2022	16,857
2023	16,056
Thereafter	132,732
Total	213,138
Lease Intangibles (Below-Market)
Year Ending December 31,
2019	(3,397)
2020	(4,432)
2021	(4,109)
2022	(3,210)
2023	(2,639)
Thereafter	(10,086)
Total	$ (27,873)