Earnings Per Share - Additional Information (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 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	72,984	164,341	36,648	82,165
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			1,209	579
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	8,585,294	10,704,794	8,910,315	10,828,471