Valuation And Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance For Doubtful Accounts [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$ 7,516	$ 6,700	$ 6,072
Charged to costs and expenses	2,361	4,255	2,427
Deductions	3,022	3,439	1,799
Balance at end of period	6,855	7,516	6,700
Tax Valuation Allowance [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	15,587	25,979	27,230
Charged to costs and expenses	0	0	0
Deductions	2,800	10,392	1,251
Balance at end of period	$ 12,787	$ 15,587	$ 25,979