Equity - Schedule of Movement in Outstanding Shares of Class A Common Stock, Restricted Class A Common Stock and Deferred Stock Units (Parenthetical) (Detail) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Class A Common Stock [Member]
Class of Stock [Line Items]
Deferred stock units held by directors	328,065	281,143
Common stock, shares issued under dividend reinvestment program	949	971
Restricted Stock [Member]
Class of Stock [Line Items]
Restricted Class A Common Stock, Forfeited	28,971
Restricted Stock [Member] | Class A Common Stock [Member]
Class of Stock [Line Items]
Restricted Class A Common Stock, Forfeited	28,971	249