Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended				9 Months Ended		12 Months Ended
	Aug. 18, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Class of Stock [Line Items]
Issuance of common stock, net, shares	16,330
Proceeds from the issuance of common stock, net	$ 163,700					$ 163,466	$ 0
Share price to the public (in usd per share)	$ 10.50
Dividends declared per common share (in usd per share)		$ 0.16	$ 0.16	$ 0.16	$ 0	$ 0.48	$ 0	$ 0.125
Dividend, payable date						Apr. 15, 2015
Dividend, record date						Mar. 31, 2015
Over-Allotment Option [Member]
Class of Stock [Line Items]
Issuance of common stock, net, shares	2,130