Stock Transactions and Unit Redemptions - Additional Information (Details) $ / shares in Units, $ in Thousands	3 Months Ended			9 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($) vote class $ / shares shares	Jun. 30, 2020 $ / shares shares	Mar. 31, 2020 $ / shares	Sep. 30, 2020 USD ($) vote class shares $ / shares	Dec. 31, 2019 USD ($) $ / shares shares	Sep. 30, 2019 shares	Jun. 30, 2019 shares	Dec. 31, 2018 shares	Aug. 01, 2018 USD ($)
Class of Stock
Number of authorized classes of common stock | class	2			2
Shares repurchased (in shares)	4,568,002			4,568,002	4,568,002
Class A Common Stock
Class of Stock
Common stock, votes per share | vote	1			1
Common stock, shares authorized (in shares)	1,000,000,000			1,000,000,000	1,000,000,000
Common stock, par value (in usd per share) | $ / shares	$ 0.01			$ 0.01	$ 0.01
Common stock, shares outstanding (in shares)	158,630,125	157,811,436		158,630,125	156,265,461	154,989,126	156,679,527	156,916,336
Shares repurchased (in shares)	4,568,002			4,568,002	4,568,002
Shares repurchased price (in dollars per share) | $ / shares	$ 0	$ 0	$ 0	$ 9.32	$ 9.32
Share repurchase and redemption unit remaining authorized amount | $	$ 157,413			$ 157,413	$ 157,413
Class A Common Stock | Maximum | Limited Partnership Interests or Other Equity Interests in Subsidiaries | Affiliated Persons or Entities
Class of Stock
Stock repurchases and redeemed or repurchases authorized amount | $									$ 200,000
Class B Common Stock
Class of Stock
Common stock, votes per share | vote	10			10
Common stock, shares authorized (in shares)	500,000,000			500,000,000	500,000,000
Common stock, par value (in usd per share) | $ / shares	$ 0.01			$ 0.01	$ 0.01
Conversion of common stock (in shares)				1
Common stock, shares outstanding (in shares)	21,285,533			21,285,533	21,285,533	21,300,000