Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 03, 2017	Jun. 15, 2017	Jan. 27, 2015	Aug. 03, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2017
Subsequent Event [Line Items]
Dividend declared common share, per share		$ 0.15			$ 0.15	$ 0.15
Twenty Fifteen Dividend Reinvestment And Stock Purchase Plan
Subsequent Event [Line Items]
Issuance of stock (in shares)							52,686
Common stock issued, weighted average price per share							$ 5.88
Proceeds from issuance of common stock							$ 310
Series B Preferred Stock
Subsequent Event [Line Items]
Conversion rate of preferred stock to common stock							4.8469%
Series C Preferred Stock
Subsequent Event [Line Items]
Issuance of stock (in shares)			300,000
Proceeds on Series C Preferred Stock issued					$ (22,065)		$ (26,920)
Series C Preferred Stock | FBR Sales Agreement
Subsequent Event [Line Items]
Issuance of stock (in shares)							896,645
Proceeds on Series C Preferred Stock issued							$ 22,100
Subsequent Event | Twenty Fifteen Dividend Reinvestment And Stock Purchase Plan
Subsequent Event [Line Items]
Issuance of stock (in shares)				53,377
Common stock issued, weighted average price per share				$ 5.92
Proceeds from issuance of common stock				$ 316
Subsequent Event | Series B Preferred Stock
Subsequent Event [Line Items]
Conversion rate of preferred stock to common stock	4.8804%
Subsequent Event | Series C Preferred Stock
Subsequent Event [Line Items]
Issuance of stock (in shares)				75,422,000
Preferred Stock issued, weighted average price per share				$ 25.09
Proceeds on Series C Preferred Stock issued				$ 1,870