Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended		2 Months Ended	3 Months Ended
	Mar. 15, 2018	Feb. 15, 2018	Dec. 31, 2017	Aug. 31, 2017	Sep. 27, 2017	Mar. 31, 2018	Mar. 31, 2017	Sep. 28, 2017
Class of Stock
Equity distribution agreement, authorized (in shares)			17,000,000
Common stock dividend declared (dollars per share)						$ 0.42	$ 0.4000
Common Stock
Class of Stock
Repurchase of shares of common stock (in shares)						0	0
Remaining number of shares authorized to be repurchased (in shares)						18,239,082
Common stock dividend declared (dollars per share)	$ 0.42
Preferred Stock
Class of Stock
Preferred stock, redemption price per share (dollars per share)						$ 25
Series A Preferred Stock
Class of Stock
Preferred stock dividend rate						7.75%
Preferred stock, liquidation preference (dollars per share)						$ 25
Preferred stock, dividends per annum (dollars per share)						$ 1.9375
Preferred stock dividend (dollars per share)	$ 0.4844
Series B Preferred Stock
Class of Stock
Preferred stock dividend rate						7.75%
Preferred stock, liquidation preference (dollars per share)						$ 25
Preferred stock, dividends per annum (dollars per share)						$ 1.9375
Preferred stock dividend (dollars per share)		$ 0.4844
Series C Preferred Stock
Class of Stock
Preferred stock dividend rate				7.50%
Preferred stock, liquidation preference (dollars per share)				$ 25
Preferred stock, dividends per annum (dollars per share)					$ 1.875
Proceeds from issuance of preferred stock, net of offering costs				11,500,000
Preferred stock dividend (dollars per share)		$ 0.46875
LIBOR | Series B Preferred Stock
Class of Stock
Preferred stock dividend variable rate spread						5.18%
LIBOR | Series C Preferred Stock
Class of Stock
Preferred stock dividend variable rate spread								5.289%
Incentive Plan
Class of Stock
Number of shares of common stock remain available for future issuance (in shares)						778,288
Total unrecognized compensation cost						$ 306
Share-based compensation cost not yet recognized, period for recognition						48 months
Weighted average remaining vesting period						23 months
Incentive Plan | Common Stock
Class of Stock
Common stock options reserved for issuance (in shares)						1,000,000
Compensation expense recognized						$ 93	$ 85
Restricted stock issued (in shares)						7,177	5,456
Incentive Plan | Common Stock | Employee
Class of Stock
Compensation expense recognized						$ 14	$ 31