Nature of Business and Financial Statement Presentation - Additional Information (Detail)	3 Months Ended				9 Months Ended
	Sep. 30, 2015 USD ($)	Mar. 31, 2015 USD ($) Assets	Dec. 31, 2014	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Nature Of Business And Financial Statement Presentation [Line Items]
Tax expense	$ 528,000			$ (214,000)	$ 6,001,000	$ 1,113,000
Impact on net income due to adoption of new accounting pronouncement	$ 0				$ 0
Puerto Rico Tax Restructuring [Member]
Nature Of Business And Financial Statement Presentation [Line Items]
Number of assets owned | Assets		14
Prepay of taxes		$ 20,200,000
Effective tax rate on capital gains		12.00%	29.00%
Effective tax rate		10.00%	39.00%
Taxable REIT subsidiary activity		$ 16,800,000
Tax expense		$ 3,400,000
Effective tax rate spread		2.00%