Investments - Summary of Total Impairment Losses Recognized (Details) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2019 |
Mar. 31, 2018 |
|
| Real Estate [Abstract] | ||
| Real estate and intangible asset impairment | $ 3,692 | $ 14,585 |
| Recovery of loans receivable, previously impaired | 0 | (16) |
| Total impairment loss | $ 3,692 | $ 14,569 |