Long-term Debt (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		1 Months Ended					1 Months Ended							6 Months Ended					6 Months Ended
	Jun. 25, 2011	Dec. 25, 2010	Jun. 30, 2011 6.625% senior unsecured notes due in April 2020	Apr. 30, 2010 6.625% senior unsecured notes due in April 2020	Jun. 25, 2011 6.625% senior unsecured notes due in April 2020	Dec. 25, 2010 6.625% senior unsecured notes due in April 2020	Apr. 08, 2010 6.625% senior unsecured notes due in April 2020	Jun. 30, 2011 6.875% Senior Subordinated Notes	May 31, 2004 6.875% Senior Subordinated Notes	Jun. 25, 2011 6.875% Senior Subordinated Notes	Dec. 25, 2010 6.875% Senior Subordinated Notes	May 04, 2004 6.875% Senior Subordinated Notes	Jun. 25, 2011 Revolving credit agreement	Dec. 25, 2010 Revolving credit agreement	Jun. 25, 2011 Revolving credit agreement LIBOR	Jun. 25, 2011 Revolving credit agreement Prime lending rate	Jun. 25, 2011 Revolving credit agreement Federal Funds rate	Jun. 25, 2011 IDR Bonds	Dec. 25, 2010 IDR Bonds	Jun. 25, 2011 1.75% to 3.485% notes	Dec. 25, 2010 1.75% to 3.485% notes
Long-term debt:
Unamortized premium on senior unsecured notes	$ 14,770				$ 14,770
Total long-term debt	489,402	468,834			450,000	300,000					150,000		14,000	8,000				8,500	8,500	2,132	2,334
Less current installments of long-term debt	272	238
Long-term debt, excluding current installments	489,130	468,596
Interest rate on notes (as a percent)					6.625%		6.625%			6.875%		6.875%
Aggregate principal amount					450,000
Unamortized premium balance	14,770				14,770
Debt instrument issued, face amount	150,000		150,000	300,000					150,000
Face amount of notes redeemed								150,000
Redemption price of debt instrument (as a percent)								101.46%
Debt instrument, redemption premium								1,700
Interest rate on notes, low end of the range (as a percent)																				1.75%
Interest rate on notes, high end of the range (as a percent)																				3.485%
Maximum borrowing capacity													280,000
Increase in borrowing capacity, maximum													100,000
Variable interest rate basis															LIBOR (based on a 1 week or 1, 2, 3, or 6 month interest period)
Basis points spread on variable interest rate, low end of the range (as a percent)															1.25%
Basis points spread on variable interest rate, high end of the range (as a percent)															2.00%
Basis points added to Federal Funds rate (as a percent)																	0.50%
Basis points added to the prime lending rate, or the Federal Funds rate plus 50 basis points, low end of the range (as a percent)																0.25%	0.25%
Basis points added to the prime lending rate, or the Federal Funds rate plus 50 basis points, high end of the range (as a percent)																1.00%	1.00%
Variable interest rate, base period (in weeks)	1
Outstanding borrowings													14,000
Effective interest rate (as a percent)																		0.50%	0.50%
Annual interest rate on revolving credit agreement (as a percent)													1.39%
Additional borrowing capacity													246,869
Minimum aggregate maturities of long-term debt
2012	334
2013	14,256
2014	262
2015	$ 275