Stockholders' Equity - Per share repurchase price (Details)	9 Months Ended
	Sep. 30, 2020
Less than 1 year
Class of Stock [Line Items]
Repurchase Price on Repurchase Date	No Repurchase Allowed
1 year
Class of Stock [Line Items]
Repurchase Price on Repurchase Date	92.5% of most recent per share NAV
2 years
Class of Stock [Line Items]
Repurchase Price on Repurchase Date	95.0% of most recent per share NAV
3 years
Class of Stock [Line Items]
Repurchase Price on Repurchase Date	97.5% of most recent per share NAV
4 years
Class of Stock [Line Items]
Repurchase Price on Repurchase Date	100.0% of most recent per share NAV
In the event of a stockholder's death or disability
Class of Stock [Line Items]
Repurchase Price on Repurchase Date	100.0% of most recent per share NAV