Investments - Summary of Total Impairment Losses Recognized (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Investments in and Advances to Affiliates, Schedule of Investments [Abstract] | |||
| Real estate and intangible asset impairment | $ 93,441 | $ 80,390 | $ 68,565 |
| Write-off of lease intangibles, net | 8,500 | 7,683 | 1,666 |
| Loans receivable impairment | 389 | 176 | 324 |
| Total impairments from real estate investment net assets | 102,330 | 88,249 | 70,555 |
| Other impairment | 0 | 26 | 174 |
| Total impairment loss in continuing and discontinued operations | $ 102,330 | $ 88,275 | $ 70,729 |