Schedule II - Valuation and Qualifying Accounts (Detail) - 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 Year	$ 936	$ 909	$ 909
Additions, Charged to Income	1,157	602	985
Additions, Other Accounts	136	337	340
Deductions	(1,121)	(912)	(1,325)
Balance at End of Year	$ 1,108	$ 936	$ 909