Related Party Transactions - Management Agreement (Details) - SP General Services LLC - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Related Party Transaction [Line Items]
Management fee percentage, quarterly basis (as a percent)	1.50%
Management agreement renewal, term (in years)	1 year
Notice period prior to management agreement renewal, period (in days)	60 days
Management Fee
Related Party Transaction [Line Items]
Services fees and reimbursable expenses	$ 1,772	$ 1,934
Unpaid amount for management fee	128		$ 27
Reimbursable Expenses
Related Party Transaction [Line Items]
Services fees and reimbursable expenses	942	$ 2,140
Deferred fees payable to related party	$ 967		$ 409