Equity - Schedule of Movement in Outstanding Shares of Class A Common Stock, Restricted Class A Common Stock and Deferred Stock Units (Parenthetical) (Detail) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Class A Common Stock [Member]
Class of Stock [Line Items]
Deferred stock units held by directors	318,128	268,049
Common stock, shares issued under dividend reinvestment program	515	325
Restricted Stock [Member]
Class of Stock [Line Items]
Restricted Class A Common Stock, Forfeited	13,273
Restricted Stock [Member] | Class A Common Stock [Member]
Class of Stock [Line Items]
Restricted Class A Common Stock, Forfeited	13,273	249