Stock Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
	May 18, 2016	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized shares of stock, option plan, maximum	1,700,000,000
Aggregate number of shares issued in respect of restricted stock awards	500,000
Options available for award each plan year	1,200,000
Maximum number of shares of restricted stock or shares subject to a restricted stock units award granted						50,000
Maximum number of options and SARs						100,000
Maximum number of stock options and SARs awarded						10,000
Maximum number of Shares of restricted stock or shares subject to a restricted stock units award granted to individual non-employee director						5,000
Vesting period of awards				1/3 per year
Number of Options granted				276,192
Recognition of compensation expense		$ 1,992	$ 998	$ 1,024	$ 1,680
Number of share available for grant for prior plans		0		0
Maximum term for awards granted (years)				10 years
Shares issued related stock option exercises				42,089	126,808
Total intrinsic value of options exercised				$ 630	$ 2,501
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted				97,004
Vesting period				4 years