Schedule II - Valuation and Qualifying Accounts (Detail) - SEC Schedule, 12-09, Allowance, Credit Loss [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 71	$ 88	$ 120
Additions (Recovery) to Bad Debt Expense	12	(17)	57
Charged to Other Accounts	0	0	0
Deductions	(16)	0	(89)
Balance at End of Period	$ 67	$ 71	$ 88