Subsequent Events - (Details) - USD ($) |
1 Months Ended | 6 Months Ended | |
|---|---|---|---|
Aug. 10, 2018 |
Jun. 30, 2018 |
Jun. 30, 2017 |
|
| Subsequent Event [Line Items] | |||
| Proceeds from lines of credit | $ 475,500,000 | $ 568,200,000 | |
| Unsecured Debt | |||
| Subsequent Event [Line Items] | |||
| Line of credit facility, remaining borrowing capacity | $ 453,500,000 | ||
| Unsecured Debt | Subsequent Event | |||
| Subsequent Event [Line Items] | |||
| Proceeds from lines of credit | $ 420,000,000 | ||