Investments - Schedule of Lease Intangible Assets and Liabilities, Net of Accumulated Amortization (Details) - USD ($) $ in Thousands |
Jun. 30, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Capital Leased Assets [Line Items] | ||
| Intangible lease assets, net | $ 287,607 | $ 306,252 |
| Continuing and discontinuing operations | ||
| Capital Leased Assets [Line Items] | ||
| Less: accumulated amortization | (140,321) | (271,288) |
| Intangible lease assets, net | 287,607 | 409,903 |
| Continuing and discontinuing operations | In-place leases | ||
| Capital Leased Assets [Line Items] | ||
| Intangible lease assets, gross | 368,450 | 591,551 |
| Continuing and discontinuing operations | Above-market leases | ||
| Capital Leased Assets [Line Items] | ||
| Intangible lease assets, gross | 59,478 | 89,640 |
| Continuing and discontinuing operations | Below-market leases | ||
| Capital Leased Assets [Line Items] | ||
| Intangible lease liabilities, gross | 169,149 | 216,642 |
| Less: accumulated amortization | (43,244) | (61,339) |
| Intangible lease liabilities, net | $ 125,905 | $ 155,303 |