Organization and Summary of Significant Accounting Policies (Schedule of Distributions Paid to Shareholders) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Component Of Operating Cost And Expense [Line Items]
Ordinary income	$ 0.11	$ 0.00	$ 0.00
Non-dividend distributions	$ 0.69	$ 0.74	$ 0.63
Distribution paid to shareholders	$ 0.80	$ 0.74	$ 0.63
Series A Preferred Shares[Member]
Component Of Operating Cost And Expense [Line Items]
Ordinary income	$ 2.06	$ 1.96
Non-dividend distributions		$ 0.10	$ 1.35
Distribution paid to shareholders	$ 2.06	$ 2.06	$ 1.35
Series B Preferred Shares [Member]
Component Of Operating Cost And Expense [Line Items]
Ordinary income	$ 1.84	$ 1.75
Non-dividend distributions		$ 0.09	$ 0.33
Distribution paid to shareholders	$ 1.84	$ 1.84	$ 0.33