Stock Options and Restricted Stock - Additional Information (Detail) - USD ($)		3 Months Ended		9 Months Ended
		Sep. 30, 2018		Sep. 30, 2018		Jun. 30, 2018	Jun. 15, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 01, 2016	Feb. 29, 2016	Jun. 16, 2006
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option outstanding		144,666	[1]	144,666	[1]	129,666		320,626	320,626	345,518
Stock option exercisable	[1]	79,778		79,778
Unvested shares of common stock outstanding		64,888		64,888		53,666		46,666
Intrinsic value of options vested		$ 10,000		$ 24,000
2006 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of maximum number of shares approved													800,000
Number of additional shares available for issuance		0		0
Amended Director Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional shares available for issuance		0		0
Number of shares available for grant		200,000		200,000
Amended Director Plan [Member] | Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant		9,000		9,000
2015 Restricted Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant											700,000
Unvested shares of common stock outstanding		202,971		202,971
2018 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant		1,494,558		1,494,558			236,224
Shares were rolled into the 2018 Plan		1,455,558		1,455,558
2015 Director Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant							258,334					300,000
2015 Director Plan [Member] | Non Employee Director One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant							12,000
2006 and 2015 Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option outstanding		144,666		144,666
Stock option exercisable		79,778		79,778

[1] The aggregate intrinsic value, which represents the difference between the price of the Company's common stock at September 30, 2018 and the related exercise price of the underlying options, was $174,000 for outstanding options and $33,000 for exercisable options as of September 30, 2018. The remaining contractual life was 7.22 years for outstanding options and 5.51 years for exercisable options at September 30, 2018.