Equity - Schedule of Movement in Outstanding Shares of Class A Common Stock, Restricted Class A Common Stock and Deferred Stock Units (Parenthetical) (Detail) - shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Class A Common Stock [Member]
Class of Stock [Line Items]
Common stock, shares issued under dividend reinvestment program	1,429	1,599
Restricted Stock [Member]
Class of Stock [Line Items]
Deferred stock units held by directors	356,700	293,856
Restricted Class A Common Stock, Forfeited	29,580
Restricted Stock [Member] | Class A Common Stock [Member]
Class of Stock [Line Items]
Restricted Class A Common Stock, Forfeited	29,580	249