Organization and Summary of Significant Accounting Policies Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Allowance, Credit Loss [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	$ 3,897	$ 4,050	$ 4,205
Bad debt expense	4,164	916	1,199
Write-offs, net of recoveries	(1,879)	(1,069)	(1,354)
Balance at end of year	6,182	3,897	4,050
SEC Schedule, 12-09, Reserve, Inventory [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	6,264	6,531	6,979
Provision for inventory write-downs	3,998	2,660	2,036
Deductions for inventory write-offs	(2,536)	(2,927)	(2,484)
Balance at end of year	$ 7,726	$ 6,264	$ 6,531