Significant Credit and Revenue Concentration - Additional Information (Details) - tenant |
12 Months Ended | |
|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Revenue, Major Customer [Line Items] | ||
| Number of tenants | 419 | 450 |
| Revenues | Customer Concentration Risk | ||
| Revenue, Major Customer [Line Items] | ||
| Number of tenants | 0 | 0 |
| Revenues | Customer Concentration Risk | Minimum | ||
| Revenue, Major Customer [Line Items] | ||
| Percentage of concentration risk in largest tenant | 4.00% | 4.00% |
| Revenues | Customer Concentration Risk | Shopko | ||
| Revenue, Major Customer [Line Items] | ||
| Percentage of concentration risk in largest tenant | 7.70% | 9.00% |
| Assets, Total | Customer Concentration Risk | Shopko | ||
| Revenue, Major Customer [Line Items] | ||
| Percentage of concentration risk in largest tenant | 5.10% | 5.80% |