Equity - Schedule of Movement in Outstanding Shares of Class A Common Stock, Restricted Class A Common Stock and Deferred Stock Units (Parenthetical) (Detail) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Common stock, shares issued under dividend reinvestment program	1,070	597	6
Class A Common Stock [Member]
Class of Stock [Line Items]
Deferred stock units held by directors	169,027	141,521	118,919
Common stock, shares issued under dividend reinvestment program	1,070	597	6