Related-Party Transactions and Agreements - Related Party Costs (Details) (Affiliate, USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	$ 155,133		$ 3,650,882		$ 4,305,804
Advisor fees and expense reimbursements
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	0		3,561,608		3,720,000
Consulting fees
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	137,250		50,178		0
Office rent
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	17,883				0
Disposition fees
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	0		39,096		219,449
Commissions
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	0	[1],[2]	0	[1],[2]	246,546	[1],[2]
Dealer-manager fees
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	0	[2]	0	[2]	71,057	[2]
Other offering costs
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	$ 0	[2]	$ 0	[2]	$ 48,752	[2]

[1] Substantially all commissions were re-allowed to participating broker/dealers.

[2] Commissions, dealer-manager fees, and other offering costs were charged against stockholders’ equity as incurred.