Long-Term Debt (Mortgage Notes Payable) - Additional Information (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2014 USD ($) Property	Dec. 31, 2015 USD ($) Building Property	Mar. 08, 2013 USD ($)	Feb. 22, 2013 USD ($)
UBS Mortgage Note Payable [Member]
Debt Instrument [Line Items]
Mortgage Note Payable		$ 7,300,000
BOA Mortgage Note Payable [Member]
Debt Instrument [Line Items]
Mortgage Note Payable		23,100,000
Wells Fargo Mortgage Note Payable [Member]
Debt Instrument [Line Items]
Mortgage Note Payable		$ 30,000,000
Mortgage Notes Payable [Member] | UBS Mortgage Note Payable [Member]
Debt Instrument [Line Items]
Mortgage Note Payable				$ 7,300,000
Maturity period		2018-02
Interest rate on mortgage loan		3.655%
Date of acquisition		Jan. 31, 2013
Mortgage Notes Payable [Member] | UBS Mortgage Note Payable [Member] | Hilton Resorts Corporation [Member]
Debt Instrument [Line Items]
Number of office building | Building		2
Mortgage Notes Payable [Member] | BOA Mortgage Note Payable [Member]
Debt Instrument [Line Items]
Mortgage Note Payable			$ 23,100,000
Maturity period		2023-04
Interest rate on mortgage loan		3.67%
Number of income properties | Property		14
Mortgage Notes Payable [Member] | Wells Fargo Mortgage Note Payable [Member]
Debt Instrument [Line Items]
Mortgage Note Payable	$ 30,000,000
Maturity period	2034-10
Interest rate on mortgage loan	4.33%
Number of income properties | Property	6
Mortgage loan payment terms		The mortgage loan matures in October 2034, and carries a fixed rate of 4.33% per annum during the first ten years of the term, and requires payments of interest only during the first ten years of the loan. After the tenth anniversary of the effective date of the loan the cash flows generated by the underlying six income properties must be used to pay down the principal balance of the loan until paid off or until the loan matures. The loan is fully pre-payable after the tenth anniversary date of the effective date of the loan.