Earnings (Loss) Per Class A Share - Computation of Basic and Diluted Earnings (Loss) Per Class A Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Line Items]
Net Income (Loss) Attributable to Class A Shareholders	$ 51,418	$ (24,284)	$ 18,222
Net Income (Loss) Attributable to Class A Shareholders, Diluted	$ 72,887	$ (24,284)	$ 18,222
Weighted-Average Class A Shares Outstanding, Basic (in shares)	20,773,493	19,270,929	18,642,379
Weighted-Average Class A Shares Outstanding, Diluted (in shares)	46,300,690	19,270,929	18,718,176
Earnings (Loss) Per Class A Share, Basic (in dollars per share)	$ 2.48	$ (1.26)	$ 0.98
Earnings (Loss) Per Class A Share, Diluted (in dollars per share)	$ 1.57	$ (1.26)	$ 0.97
Group A Units
Earnings Per Share [Line Items]
Net Income (Loss) Attributable to Class A Shareholders, Effect of dilutive securities	$ 21,469	$ 0	$ 0
Weighted-Average Class A Shares Outstanding, Effect of dilutive securities (in shares)	16,976,983	0	0
Number of Antidilutive Units Excluded from Diluted Calculation (in shares)	0	26,073,057	27,230,147
Group E Units
Earnings Per Share [Line Items]
Weighted-Average Class A Shares Outstanding, Effect of dilutive securities (in shares)	7,817,696
Number of Antidilutive Units Excluded from Diluted Calculation (in shares)	0
RSUs
Earnings Per Share [Line Items]
Net Income (Loss) Attributable to Class A Shareholders, Effect of dilutive securities	$ 0	$ 0	$ 0
Weighted-Average Class A Shares Outstanding, Effect of dilutive securities (in shares)	732,518	0	75,797
Number of Antidilutive Units Excluded from Diluted Calculation (in shares)	0	4,826,130	0