Stockholders' Equity - Treasury Stock (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2018
Equity, Class of Treasury Stock [Line Items]
Shares purchased during period (shares)	501,782	127,792
Total number of shares purchased (shares)	629,574		629,574
Average price paid per share (usd per share)	$ 14.99	$ 15.04
Average price paid per share (usd per share)	$ 15.00		$ 15.00
Treasury stock acquired during period			$ 9,467,000
Commissions paid to acquire shares			$ 25,183
Common Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Shares purchased during period (shares)	501,782	127,792
Total number of shares purchased (shares)	629,574		629,574
Treasury stock acquired during period	$ 558,000	$ 8,077,000