Stockholders' Equity - Summary of Shares Issued and Held in Treasury or Outstanding (Detail) - shares	Mar. 31, 2021	Dec. 31, 2020
Class A Common Stock [Member]
Class of Stock [Line Items]
Common stock - issued	17,301,199	17,224,830
Common stock - held in treasury	(2,917,286)	(2,684,274)
Common stock - outstanding	14,383,913	14,540,556
Class B Common Stock [Member]
Class of Stock [Line Items]
Common stock - issued	234,903	234,903
Common stock - held in treasury	(234,903)	(234,903)
Common stock - outstanding	0	0