Income Taxes: Effective tax rate (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income (Loss) from Continuing Operations Attributable to Parent [Abstract]
Income from continuing operations, United States	$ 62,204,000	$ 63,575,000	$ 46,669,000
Income from continuing operations, foreign	(365,000)	2,847,000	1,116,000
Income from continuing operations	61,839,000	66,422,000	47,785,000
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Income Tax Reconciliation, Income Tax Expense (Benefit), at Federal Statutory Income Tax Rate	21,644,000	23,247,000	16,724,000
Income Tax Reconciliation, State and Local Income Taxes	1,356,000	1,460,000	1,007,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate	35.00%	35.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes	2.20%	2.20%	2.10%
Income Tax Reconciliation, Tax Credits	(1,465,000)	(1,171,000)	(121,000)
Effective Income Tax Rate Reconciliation, Tax Credits	(2.40%)	(1.80%)	(0.30%)
Income Tax Reconciliation, Tax Exempt Income	(23,000)	(45,000)	(33,000)
Income Tax Reconciliation, Deductions, Qualified Production Activities	(1,559,000)	(1,508,000)	(997,000)
Effective Income Tax Rate Reconciliation, Tax Exempt Income	(0.10%)	(0.10%)	(0.10%)
Effective Income Tax Rate Reconciliation, Deductions, Qualified Production Activities	(2.50%)	(2.30%)	(2.00%)
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential	1.00%	(0.30%)	2.70%
Income Tax Reconciliation, Foreign Income Tax Rate Differential	605,000	(230,000)	1,282,000
Effective Income Tax Rate, Continuing Operations	33.20%	32.70%	37.40%
Deferred Tax Assets, Net, Current Classification [Abstract]
Deferred Tax Assets, Net, Current	4,293,000	4,081,000
Deferred Tax Assets, Net, Noncurrent Classification [Abstract]
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent	5,642,000	4,759,000
Deferred Tax Liabilities [Abstract]
Noncurrent deferred tax liability	(5,247,000)	(7,144,000)
Income Tax Expense (Benefit) [Abstract]
Current Federal Tax Expense (Benefit)	21,072,000	19,246,000	15,331,000
Current State and Local Tax Expense (Benefit)	2,080,000	1,246,000	1,200,000
Current Foreign Tax Expense (Benefit)	678,000	785,000	1,109,000
Current Income Tax Expense (Benefit)	23,830,000	21,277,000	17,640,000
Deferred Federal Income Tax Expense (Benefit)	(2,276,000)	169,000	(781,000)
Deferred State and Local Income Tax Expense (Benefit)	(796,000)	326,000	439,000
Deferred Foreign Income Tax Expense (Benefit)	(200,000)	(19,000)	564,000
Income Tax Expense (Benefit)	20,558,000	21,753,000	17,862,000
Deferred Income Tax Expense (Benefit)	(3,272,000)	476,000	222,000
Tax Benefit from Stock Options Exercised	4,600,000	4,300,000	1,700,000
Increase (Decrease) in Income Taxes Payable	700,000
Deferred tax liability, Mexican subsidiary	2,300,000
Unrecognized Tax Benefits [Abstract]
Unrecognized Tax Benefits	4,978,000	4,411,000	5,306,000
Unrecognized Tax Benefits, Increases Resulting from Prior Period Tax Positions	156,000	494,000	(649,000)
Unrecognized Tax Benefits, Increases Resulting from Current Period Tax Positions	490,000	764,000	518,000
Unrecognized Tax Benefits, Decreases Resulting from Settlements with Taxing Authorities	(230,000)	(392,000)	(764,000)
Unrecognized Tax Benefits, Reductions Resulting from Lapse of Applicable Statute of Limitations	(1,158,000)	(299,000)	0
Unrecognized Tax Benefits	4,236,000	4,978,000	4,411,000
Undistributed foreign subsidiaries earnings	13,500,000	14,000,000
State income taxes [Member]
Deferred Tax Assets, Net, Current Classification [Abstract]
Deferred Tax Assets, Gross, Current	437,000	343,000
Deferred Tax Liabilities [Abstract]
Noncurrent deferred tax liability	1,751,000	(1,481,000)
Foreign Country [Member]
Deferred Tax Assets, Net, Current Classification [Abstract]
Deferred Tax Assets, Gross, Current	400,000	429,000
Deferred Tax Assets, Net, Noncurrent Classification [Abstract]
Deferred Income Taxes and Other Assets, Noncurrent	983,000	526,000
Deferred Tax Liabilities [Abstract]
Noncurrent deferred tax liability	2,301,000	2,633,000
Accruals other [Member]
Deferred Tax Assets, Net, Current Classification [Abstract]
Deferred Tax Assets, Gross, Current	1,881,000	1,377,000
Deferred Tax Assets, Net, Noncurrent Classification [Abstract]
Deferred Income Taxes and Other Assets, Noncurrent	536,000	347,000
Deferred Tax Liabilities [Abstract]
Noncurrent deferred tax liability	186,000	186,000
Tax credits [Member]
Deferred Tax Assets, Net, Current Classification [Abstract]
Deferred Tax Assets, Gross, Current	441,000	452,000
Allowance for Doubtful Accounts [Member]
Deferred Tax Assets, Net, Current Classification [Abstract]
Deferred Tax Assets, Gross, Current	101,000	102,000
Inventory Valuation Reserve [Member]
Deferred Tax Assets, Net, Current Classification [Abstract]
Deferred Tax Assets, Gross, Current	1,247,000	1,378,000
Current deferred tax asset [Member]
Deferred Tax Assets, Net, Current Classification [Abstract]
Deferred Tax Assets, Gross, Current	4,507,000	4,081,000
Valuation allowance of deferred tax assets, current [Member]
Deferred Tax Assets, Net, Current Classification [Abstract]
Deferred Tax Assets, Valuation Allowance	(214,000)	0
Depreciation and Amortization [Member]
Deferred Tax Assets, Net, Noncurrent Classification [Abstract]
Deferred Income Taxes and Other Assets, Noncurrent	(458,000)	(523,000)
Deferred Tax Liabilities [Abstract]
Noncurrent deferred tax liability	6,429,000	6,862,000
Tax credits state [Member]
Deferred Tax Assets, Net, Noncurrent Classification [Abstract]
Deferred Income Taxes and Other Assets, Noncurrent	4,927,000	4,409,000
Non-current deferred tax asset, gross total [Member]
Deferred Tax Assets, Net, Noncurrent Classification [Abstract]
Deferred Income Taxes and Other Assets, Noncurrent	5,988,000	4,759,000
Valuation allowance of deferred tax assets, noncurrent [Member]
Deferred Tax Assets, Net, Current Classification [Abstract]
Deferred Tax Assets, Valuation Allowance	(346,000)	0
Acquired future tax deductions [Member]
Deferred Tax Liabilities [Abstract]
Noncurrent deferred tax liability	515,000	460,000
Stock-based compensation [Member]
Deferred Tax Liabilities [Abstract]
Noncurrent deferred tax liability	(5,581,000)	(3,843,000)
Foreign currency translation adjustments [Member]
Deferred Tax Liabilities [Abstract]
Noncurrent deferred tax liability	(354,000)	(635,000)
Noncurrent deferred tax liability [Member]
Deferred Tax Liabilities [Abstract]
Noncurrent deferred tax liability	5,247,000	7,144,000
Allowance for Doubtful Accounts [Member]
Income Tax Expense (Benefit) [Abstract]
Deferred Income Tax Expense (Benefit)	(59,000)	(24,000)	(66,000)
Inventory Valuation Reserve [Member]
Income Tax Expense (Benefit) [Abstract]
Deferred Income Tax Expense (Benefit)	143,000	1,147,000	(1,137,000)
Accruals other [Member]
Income Tax Expense (Benefit) [Abstract]
Deferred Income Tax Expense (Benefit)	(2,375,000)	(464,000)	(1,792,000)
State and Local Jurisdiction [Member]
Income Tax Expense (Benefit) [Abstract]
Deferred Income Tax Expense (Benefit)	177,000	(7,000)	(290,000)
Acquired future tax deductions [Member]
Income Tax Expense (Benefit) [Abstract]
Deferred Income Tax Expense (Benefit)	50,000	293,000	300,000
Depreciation and Amortization [Member]
Income Tax Expense (Benefit) [Abstract]
Deferred Income Tax Expense (Benefit)	(700,000)	(205,000)	2,820,000
Tax credits [Member]
Income Tax Expense (Benefit) [Abstract]
Deferred Income Tax Expense (Benefit)	$ (508,000)	$ (264,000)	$ 387,000