Organization and Summary of Significant Accounting Policies (Schedule of Effects of Change in Accounting for Inventory on the Statement of Income (Loss)) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales									$ 406,081	$ 376,158	$ 348,945
Income from continuing operations, net of tax									46,320	53,412	38,203
Net income									$ 46,320	$ 53,412	$ 38,305
Basic earnings per share (in dollars per share)									$ 2.52	$ 2.94	$ 2.23
Diluted earnings per share (in dollars per share)									$ 2.48	$ 2.86	$ 2.16
Change from LIFO to FIFO
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales										$ 376,158	$ 348,945
Income from continuing operations, net of tax	$ 6,577	$ 12,546	$ 13,554	$ 13,643	$ 7,247	$ 20,407	$ 11,056	$ 14,702		53,412	38,203
Net income										$ 53,412	$ 38,305
Basic earnings per share (in dollars per share)										$ 2.94	$ 2.23
Diluted earnings per share (in dollars per share)										$ 2.86	$ 2.16
Scenario, Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income from continuing operations, net of tax	$ 6,577	$ 12,455	$ 13,540	$ 13,627	$ 7,013	$ 20,388	$ 10,902	$ 14,580
Scenario, Previously Reported | Change from LIFO to FIFO
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales										$ 376,972	$ 349,782
Income from continuing operations, net of tax										52,883	37,659
Net income										$ 52,883	$ 37,761
Basic earnings per share (in dollars per share)										$ 2.91	$ 2.20
Diluted earnings per share (in dollars per share)										$ 2.83	$ 2.13
Restatement Adjustment | Change from LIFO to FIFO
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales										$ (814)	$ (837)
Income from continuing operations, net of tax										529	544
Net income										$ 529	$ 544
Basic earnings per share (in dollars per share)										$ 0.03	$ 0.03
Diluted earnings per share (in dollars per share)										$ 0.03	$ 0.03