Shareholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
	Dec. 31, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Shareholders Equity [Line Items]
Discount on common stock		$ 2,447		$ 2,447
Underwriter fees		150
Stock issuance cost		$ 253
Equity Distribution Agreement [Member]
Shareholders Equity [Line Items]
Stock issuance cost			$ 82
Net sales commissions			$ 299
Shares sold under equity distribution agreement	0
Common Stock [Member]
Shareholders Equity [Line Items]
Issuance of common stock		1,233,000		1,418,000	342,000
Common stock price per share		$ 30.00		$ 30.00
Cash proceeds from sale of common stock		$ 39,953
Common Stock [Member] | Equity Distribution Agreement [Member]
Shareholders Equity [Line Items]
Issuance of common stock			342,000
Cash proceeds from sale of common stock			$ 12,978
Weighted average price per share			$ 38.83
Over Allotment Option [Member] | Common Stock [Member]
Shareholders Equity [Line Items]
Issuance of common stock		185,000