Valuation And Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance For Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	$ 828	$ 426	$ 586
Additions	320	1,010	786
Deductions	60	608	946
Balance at end of year	1,088	828	426
Tax Valuation Allowance [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	10,593	11,530	15,936
Additions
Deductions	3,723	937	4,406
Balance at end of year	$ 6,870	$ 10,593	$ 11,530