Equity - Summary of Authorized and Outstanding Equity (Detail) - shares	9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Preferred shares
Preferred stock, shares authorized	10,000,000			10,000,000
Preferred stock, shares outstanding	0			0
Class A Common Stock
Common shares
Common stock, shares authorized	50,000,000			50,000,000
Common stock, shares outstanding	9,544,607	9,520,000	9,506,000	9,329,879	9,180,000	8,624,000	8,535,000	8,518,000
Common stock, voting rights	one vote for each share
Class B Common Stock
Common shares
Common stock, shares authorized	25,000,000			25,000,000
Common stock, shares outstanding	4,827,731	4,852,000	4,855,000	5,031,017	5,181,000	4,833,000	4,919,000	4,934,000
Common stock, voting rights	one vote for each share