Earnings Per Share - Additional Information (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Stock Options
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive securities excluded from the calculation of earnings per share	76,455	36,342	50,063	114,628
Restricted Stock Units
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive securities excluded from the calculation of earnings per share	713	0	1,688	11,245
Holdings Units
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Shares exchanged for Class A common stock			1
Class B Common Stock
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Shares exchanged for Class A common stock			1
Class B Common Stock | Equity Unit Purchase Agreements
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive securities excluded from the calculation of earnings per share	8,579,094	10,004,682	8,798,695	10,550,857