Schedule II - Valuation and Qualifying Accounts (Details) - SEC Schedule, 12-09, Allowance, Credit Loss [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
End of year balance	$ 1,631	$ 1,601	$ 1,300	$ 1,810
Charged to operations	323	768	662
Credited to operations	0	0	0
Written off	$ (293)	$ (467)	$ (1,172)