Intangible Lease Liabilities, Net (Schedule of Intangible Lease Liabilities, Net) (Details) - USD ($) $ in Thousands |
3 Months Ended | 12 Months Ended | |
|---|---|---|---|
Mar. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Intangible Lease Liabilities, Net [Abstract] | |||
| Below-market leases, net of accumulated amortization | $ 56,374 | $ 57,606 | $ 61,294 |
| Below-market leases, accumulated amortization | $ 8,824 | $ 7,592 | $ 2,760 |
| Below market leases, weighted average remaining life | 17 years 4 months 24 days | 17 years 7 months 6 days | 18 years 8 months 12 days |