Stock Transactions and Unit Redemptions - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended		9 Months Ended
	Mar. 09, 2018	Dec. 13, 2017	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Aug. 01, 2018
Class of Stock [Line Items]
Stock repurchase program and unit redemption remaining authorized amount			$ 251,206		$ 251,206
CF & Co [Member]
Class of Stock [Line Items]
Common stock, issued during the period			0	0	200,000	900,000
Payment percentage of the gross proceeds from the sale of shares		5.50%
Aggregate proceeds from issuance of common stock					$ 700	$ 5,300
Weighted-average price per share					$ 4.04	$ 6.17
Maximum [Member]
Class of Stock [Line Items]
Payment percentage of the gross proceeds from the sale of shares	2.00%
Class B Common Stock [Member]
Class of Stock [Line Items]
Common stock, issued during the period			0	0	0	0
Common stock outstanding			45,884,380		45,884,380		45,884,380
Common stock, shares issued			45,884,000		45,884,000		45,884,000
Common stock value issued			$ 459		$ 459		$ 459
Class A Common Stock [Member]
Class of Stock [Line Items]
Common stock, issued during the period			91,034	53,810	339,617	162,237
Common stock outstanding			315,315,000		315,315,000		307,915,000
Common stock, shares issued			365,842,000		365,842,000		358,440,000
Common stock value issued			$ 3,658		$ 3,658		$ 3,584
Company's repurchase and additional redemption authority amount								$ 300,000
Stock repurchase program and unit redemption remaining authorized amount			$ 251,200		$ 251,200
Class A Common Stock [Member] | CF & Co [Member]
Class of Stock [Line Items]
Common stock, issued during the period			0
Class A Common Stock [Member] | New CEO Program [Member]
Class of Stock [Line Items]
Maximum amount under the controlled equity offering program	$ 300,000
Common stock, shares issued			17,600,000		17,600,000
Common stock value issued			$ 210,600		$ 210,600