Schedule II - Valuation and Qualifying Account (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Movement In Valuation Allowances And Reserves Roll Forward
Reserve for doubtful accounts, start	$ 2,650	$ 2,590	$ 3,139
Additions charged to / recovered from expense	594	605	(202)
Write-offs	(454)	(560)	(428)
Other	(60)	15	81
Reserve for doubtful accounts, end	$ 2,730	$ 2,650	$ 2,590