Stock Transactions and Unit Redemptions - The Unit Redemptions and Share Repurchases of Class A Common Stock (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended			9 Months Ended
	Jul. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2020	Sep. 30, 2019
Stock Transactions Parenthetical Disclosures [Abstract]
Redemptions, Number of Units		1,481,000	103,000	235,000	1,819,000
Repurchases, Number of Shares	2,000	2,259			2,259	233,172
Total Number of Units Redeemed or Shares Repurchased					1,821,000
Redemptions, Weighted Average Price Paid per Unit or Share		$ 2.80	$ 3.05	$ 4.30	$ 3.01
Repurchases, Weighted Average Price Paid per Unit or Shares	$ 2.58				2.58
Total Redemptions and Repurchases, Weighted Average Price Paid per Unit or Shares					$ 3.01
Total Redemptions and Repurchases, Approximate Dollar Value of Units and Shares That May Yet Be Redeemed/Purchased Under the Program		$ 251,206			$ 251,206