Common Stock and Other Equity Related Transactions - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands					6 Months Ended
	Jul. 08, 2016	Jun. 30, 2016	Apr. 08, 2016	Mar. 31, 2016	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	May 04, 2015
Class of Stock [Line Items]
Common stock, dividends paid (usd per share)			$ 0.425
Common Stock, par or stated value per share (usd per share)						$ 0.01	$ 0.01
Commissions paid to sales agents					$ 824	$ 323
6.75% Series C Cumulative Redeemable Perpetual Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends paid (usd per share)		$ 0.421875		$ 0.421875
Subsequent Event
Class of Stock [Line Items]
Common stock, dividends paid (usd per share)	$ 0.4250
Private Placement
Class of Stock [Line Items]
Aggregate Offering price								$ 125,000
Total gross proceeds					50,000
Common stock remained available for issuance		$ 75,000			$ 75,000
Private Placement | Common Stock
Class of Stock [Line Items]
Shares of common stock sold (shares)					683,548
Weighted average price per share (usd per share)					$ 73.15
Commissions paid to sales agents					$ 657