Financial Instruments And Concentration Of Credit Risk (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Concentration Risk [Line Items]
Concentration Risk Customer Accounts Receivable		One of the most significant credit risks is the ultimate realization of accounts receivable. This risk is mitigated by (i) sales to well established companies, (ii) ongoing credit evaluation of customers, and (iii) frequent contact with customers, thus enabling management to monitor current changes in business operations and to respond accordingly. Management considers these concentrations of credit risks in establishing our allowance for doubtful accounts and believes these allowances are adequate. The Company had one customer whose gross accounts receivable exceeded 10% of total gross accounts receivable as of December 31, 2018.
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Unrealized gain on derivative, net of tax		$ (1,362)	$ 1,192	$ 286
Interest expense		(10,473)	(9,405)	(9,304)
Amounts reclassified from accumulated other comprehensive loss		(236)	0	(1)
Derivative instruments, net of tax [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Amounts reclassified from accumulated other comprehensive loss		(236)	0	$ 0
Interest Rate Swap [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Interest rate swap notional amount	$ 150,000	$ 150,000	$ 155,300
Fixed interest rate	2.928%	2.928%	1.4935%
Fair value of interest rate swap	$ 3,000	$ 3,000	$ 2,000
Unrealized gain on interest rate swap		1,500	1,500
Unrealized gain on derivative, net of tax		$ 1,100	$ 900
Interest Rate Swap [Member] | Derivative instruments, net of tax [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Unrealized gain on interest rate swap	300
Unrealized gain on derivative, net of tax	200
Gain Loss On Contract Termination	3,500
Reclassification Out Of Accumulated Other Comprehensive Loss [Member] | Derivative instruments, net of tax [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Interest expense	$ (300)
Accounts Receivable [Member] | Largest Customer Accounts Receivable [Member]
Concentration Risk [Line Items]
Concentration risk, percentage		19.00%