Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
United States	$ 234,646	$ 203,269	$ 178,497
Foreign	6,732	4,881	2,888
Total	241,378	208,150	181,385
Current [Abstract]
Federal	77,000	65,676	54,447
State and other	12,182	10,263	9,126
Current tax	89,182	75,939	63,573
Deferred [Abstract]
Federal	4,079	4,568	6,942
State and other	(330)	(370)	44
Deferred tax	3,749	4,198	6,986
Total	$ 92,931	$ 80,137	$ 70,559
Reconciliation of U.S. federal statutory tax rate to effective tax rate [Abstract]
Federal statutory rate (in hundredths)	35.00%	35.00%	35.00%
Change in valuation allowance (in hundredths)	0.10%	0.20%	0.43%
Other, primarily state income tax rate (in hundredths)	3.40%	3.30%	3.47%
Total effective tax rate (in hundredths)	38.50%	38.50%	38.90%
Deferred tax assets [Abstract]
Product inventories	$ 7,010	$ 7,101
Accrued expenses	3,978	3,303
Allowance for doubtful accounts	396	606
Total current	11,384	11,010
Component reclassified for net presentation	(5,368)	(5,480)
Total current, net	6,016	5,530
Leases	1,920	1,786
Share-based compensation	13,778	13,422
Uncertain tax positions	2,746	2,092
Net operating losses	5,735	5,485
Interest rate swaps	674	1,513
Other	2,465	1,159
Total noncurrent	27,318	25,457
Less: Valuation allowance, non-current	(5,735)	(5,485)
Component reclassified for net presentation	(20,781)	(18,755)
Total non-current, net	802	1,217
Total deferred tax assets	6,818	6,747
Deferred tax liabilities [Abstract]
Trade discounts on purchases	2,698	3,001
Prepaid expenses	2,670	2,479
Total current	5,368	5,480
Component reclassified for net presentation	(5,368)	(5,480)
Total current, net	0	0
Intangible assets, primarily goodwill	42,930	40,197
Depreciation	12,326	8,366
Total non-current	55,256	48,563
Component reclassified for net presentation	(20,781)	(18,755)
Total non-current, net	34,475	29,808
Deferred Tax Liabilities, Gross	34,475	29,808
Net deferred tax liability	27,657	23,061
Loss Carryforwards [Line Items]
Excess Tax Benefit (Tax Deficiency) from Share-based Compensation, Financing Activities	7,370	7,706	$ 5,524
Uncertain tax positions activity [Roll Forward]
Beginning balance	5,978	4,690	3,837
Increases for tax positions taken during a prior period	10	410	0
Increases for tax positions taken during the current period	2,819	1,782	1,664
Decreases resulting from the expiration of the statute of limitations	961	904	811
Decreases relating to settlements	0	0	0
Ending balance	7,846	5,978	$ 4,690
Unrecognized tax benefits that, if recognized, would decrease the effective tax rate	5,100	3,886
Interest expense related to unrecognized tax benefits	156	136
Accrued interest on unrecognized tax benefits	685	529
International Subsidiaries [Member]
Loss Carryforwards [Line Items]
Tax loss carry-forwards	22,158
Deferred tax asset, valuation allowance	$ 5,735	$ 5,485