Summary of Warrants and Related Information (Detail) - Warrant - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Warrants
Outstanding	20,000	20,000	20,000
Exercised	0	0	0
Outstanding	20,000	20,000	20,000
Exercisable at December 31, 2017	20,000
Weighted Average Exercise Price
Outstanding	$ 6.64	$ 6.64	$ 6.64
Outstanding	6.64	$ 6.64	$ 6.64
Exercisable at December 31, 2017	$ 6.64