Organization and Summary of Significant Accounting Policies 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	$ 4,050	$ 4,205	$ 4,008
Bad debt expense	916	1,199	1,110
Write-offs, net of recoveries	(1,069)	(1,354)	(913)
Balance at end of year	3,897	4,050	4,205
Inventory Valuation Reserve [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	6,531	6,979	6,403
Provision for inventory write-downs	2,660	2,036	3,043
Deductions for inventory write-offs	(2,927)	(2,484)	(2,467)
Balance at end of year	$ 6,264	$ 6,531	$ 6,979