Income tax provision (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Current tax provision [Abstract]
Federal	$ 49,702		$ 49,909		$ 37,945
State	9,168		8,424		4,323
Foreign	3,269		3,859		1,349
Total	62,139		62,192		43,617
Deferred tax provision	9,350		20,362		12,039
Provision for income taxes	71,489		82,554		55,656
Effective tax rate reconciliation [Abstract]
Income tax at federal statutory rate (in hundredths)	35.00%		35.00%		35.00%
State income tax expense, net of federal income tax benefit (in hundredths)	2.80%		2.80%		3.50%
Change in unrecognized tax benefits, including interest and penalties (in hundredths)	0.50%		(1.30%)		0.10%
Non-deductible portion of goodwill impairment charge (in hundredths) (see Note 7)	0.00%		0.00%		2.90%
Qualified production activity deduction (in hundredths)	(2.40%)		(2.40%)		(1.80%)
Impact of health care legislation on deferred income taxes (in hundredths)	(1.20%)		1.70%		0.00%
Receivables for prior year tax returns (in hundredths)	(0.80%)	[1]	0.00%	[1]	(2.20%)	[1]
Other (in hundredths)	(0.80%)		(0.80%)		(1.60%)
Income tax provision (in hundredths)	33.10%		35.00%		35.90%
Charge resulting from the Health Care and Education Reconciliation Act of 2010			4,063
Credit resulting from actions to restore a portion of the deferred tax asset attributable to the receipt of Medicare Part D subsidy payments	(2,539)
Unrecognized tax benefits [Roll forward]
Balance, beginning of period	6,538		7,978		11,457
Additions for tax positions of current year	510		641		606
Additions for tax positions of prior years	1,646		1,406		2,316
Fair value of acquired tax positions (see Note 4)			1,069
Reductions for tax positions of prior years	(219)		(2,634)		(2,152)
Settlements	(1,507)		(640)		(3,186)
Lapse of statutes of limitations	(732)		(1,282)		(1,063)
Balance, end of period	6,236		6,538		7,978
Unrecognized tax benefits [Abstract]
Amount of unrecognized tax benefits as of the balance sheet date that would positively affect income tax expense and the related effective tax rate if recognized	5,152
Accruals for interest and penalties	1,497		1,382
Expense (credit) for interest and penalties	639		(837)		(446)
Amount by which it is reasonably possible that unrecognized tax benefits will decrease within the next 12 months	4,500
Amount by which it is reasonably possible that unrecognized tax benefits will increase within the next 12 months	700
Deferred tax liabilities [Abstract]
Goodwill	40,761		34,818
Intangible assets	28,831		33,774
Property, plant and equipment	6,080		4,201
Deferred advertising costs	5,769		5,964
Early extinguishment of debt (see Note 13)	3,775		3,784
All other deferred tax liabilities	4,558		3,061
Total deferred tax liabilities	89,774		85,602
Deferred tax assets [Abstract]
Employee benefit plans	29,776		29,593
Reserves and accruals	6,574		5,457
Net operating loss and tax credit carryforwards	3,366		5,760
Inventories	2,800		2,771
Federal benefit of state uncertain tax positions	1,776		1,719
Interest rate lock agreements (see Note 6)	1,751		2,709
All other deferred tax assets	1,748		1,370
Total deferred tax assets	47,791		49,379
Valuation allowance	(608)		(1,139)
Net deferred tax assets	47,183		48,240
Tax credit carryforwards	586
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	4,088
Canada [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	3,689
State [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 19,026

[1] Relates to amendments to prior year income tax returns claiming refunds primarily associated with foreign tax returns for 2011 and federal and state income tax credits for 2009.