Schedule II - Valuation and Qualifying Accounts (Detail) - Allowance for Doubtful Accounts [Member] - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 171,000	$ 183,000	$ 198,000
Charge (Recovery) to Costs and Expenses	(22,000)	18,000	66,000
Other Charges, Deductions	4,000	(30,000)	(81,000)
Balance at End of Period	$ 153,000	$ 171,000	$ 183,000