Investments - Summary of Total Impairment Losses Recognized (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2018 |
Sep. 30, 2017 |
Sep. 30, 2018 |
Sep. 30, 2017 |
|
| Investments in and Advances to Affiliates, Schedule of Investments [Abstract] | ||||
| Real estate and intangible asset impairment | $ 1,113 | $ 32,676 | $ 16,737 | $ 82,553 |
| Write-off of lease intangibles, net | 166 | 5,061 | 477 | 5,556 |
| Recovery of loans receivable, previously impaired | 0 | 0 | (17) | 0 |
| Total impairment loss | $ 1,279 | $ 37,737 | $ 17,197 | $ 88,109 |