Equity and Noncontrolling Interest - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions		12 Months Ended
	Feb. 12, 2013	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Income attributable to noncontrolling interests		$ 12,411	$ 11,441	$ 10,463
Depositary shares outstanding (in shares)		7.2
Series C Preferred Stock
Class of Stock [Line Items]
Depository shares to cumulative redeemable preferred stock ratio		1.00%
Dividend rate on preferred stock		6.875%
Liquidation preference (in usd per share)	$ 25.00
Annual dividend on depositary shares (in usd per share)	$ 1.71875
Percentage of redeemable preferred stock	6.875%