Investments - Summary of Lease Intangible, Net (Details) - USD ($) $ in Thousands |
Dec. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Capital Leased Assets [Line Items] | ||
| Intangible lease assets, net | $ 306,252 | $ 355,718 |
| Continuing operations and discontinued operations | ||
| Capital Leased Assets [Line Items] | ||
| Less: accumulated amortization | (271,288) | (243,320) |
| Intangible lease assets, net | 409,903 | 470,276 |
| Below-market leases | 216,642 | 236,008 |
| Less: accumulated amortization | (61,339) | (53,688) |
| Intangible lease liabilities, net | 155,303 | 182,320 |
| Continuing operations and discontinued operations | In-place Leases | ||
| Capital Leased Assets [Line Items] | ||
| Intangible lease assets, gross | 591,551 | 624,723 |
| Continuing operations and discontinued operations | Above-market Leases | ||
| Capital Leased Assets [Line Items] | ||
| Intangible lease assets, gross | $ 89,640 | $ 88,873 |