Equity - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Jun. 30, 2016
Class of Stock [Line Items]
Proceeds from the issuance of common stock	$ 108,166,000	$ 106,026,000
Dividends declared per common share (in usd per share)	$ 0.185	$ 0.17	$ 0.68
Dividend, payable date	Apr. 14, 2017
Dividend, record date	Mar. 31, 2017
At-The-Market Offering [Member]
Class of Stock [Line Items]
Aggregate offering price of common stock				$ 125,000,000
Issuance of common stock, net, shares	7,174,587
Proceeds from the issuance of common stock	$ 109,800,000
Issuance costs reclassified to additional paid in capital	44,000
Remaining offering amount available	$ 1,000,000
At-The-Market Offering [Member] | Weighted Average [Member]
Class of Stock [Line Items]
Share price to the public (in usd per share)	$ 15.31