Income Taxes - Additional information (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018	Sep. 30, 2019 USD ($) agreement shares	Sep. 30, 2018	Dec. 31, 2018 USD ($)
Tax Credit Carryforward [Line Items]
Effective income tax rate	25.80%	26.00%	21.00%	23.90%
Net deferred tax assets	$ 416,678		$ 416,678		$ 412,538
Total liability related to uncertain tax positions	260		$ 260		300
Number of tax receivable agreements | agreement			2
Percentage of remaining tax savings			15.00%
Tax benefit obligation	$ 433,390		$ 433,390		$ 429,233
TRA Holders
Tax Credit Carryforward [Line Items]
Applicable tax savings	85.00%		85.00%
Decrease in deferred tax assets			$ 517
Deferred tax asset	$ 20,340		20,340
Deferred tax liability	$ 17,016		$ 17,016
Class A Common Stock
Tax Credit Carryforward [Line Items]
Number of shares exchanged | shares			885,810
Class A Common Stock | TRA Holders
Tax Credit Carryforward [Line Items]
Number of shares exchanged | shares			885,810