Investments - Summary of Total Impairment Losses Recognized (Details) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
|
| Investments in and Advances to Affiliates, Schedule of Investments [Abstract] | ||
| Real estate and intangible asset impairment | $ 14,961 | $ 35,220 |
| Write-off of lease intangibles, net | (376) | (844) |
| Recovery of loans receivable, previously impaired | (16) | 0 |
| Total impairment loss | $ 14,569 | $ 34,376 |