Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for doubtful receivables
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning of Period	$ 1,440	$ 1,507	$ 1,429
Charges to Costs and Expenses	1,036	785	541
Charges (Deductions) to Other Accounts	(11)	(58)	103
Deductions	(623)	(794)	(566)
End of Period	1,842	1,440	1,507
Tax valuation allowances
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning of Period	5,964	5,709	4,903
Charges to Costs and Expenses	3,328	3,859	886
Charges (Deductions) to Other Accounts	(75)	(192)	394
Deductions	0	(3,412)	(474)
End of Period	$ 9,217	$ 5,964	$ 5,709