Stock-based compensation (Details) (USD $)	12 Months Ended
	Dec. 28, 2012	Dec. 30, 2011	Dec. 31, 2010	Dec. 25, 2009
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Severance, impairment and other associated costs	$ 0	$ 184,000	$ 0
Income tax benefit	0	0	(646,000)
Total after-tax stock based compensation expense	1,889,000	1,823,000	1,200,000
Restricted Stock and Units activity [Abstract]
Opening nonvested at beginning of period (in shares)	580,000	420,000
Ending nonvested at end of period (in shares)	1,035,000	580,000	420,000
Stock Options Shares [Abstract]
Opening stock options outstanding (in shares)	1,252,000	157,000
Ending stock options outstanding as of end of period (in shares)	1,273,000	1,252,000	157,000
Restricted Stock [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock based compensation expense	957,000	1,054,000	1,833,000
Restricted Stock and Units activity [Abstract]
Opening nonvested at beginning of period (in shares)	580,000	420,000	330,000
Granted (in shares)	589,000	369,000	238,000
Vested (in shares)	(103,000)	(112,000)	(123,000)
Forfeited/canceled (in shares)	(31,000)	(97,000)	(25,000)
Ending nonvested at end of period (in shares)	1,035,000	580,000	420,000
Restricted Stock and Units - Weighted Average Stock Grant Price [Abstract]
Opening nonvested restricted stock and units (in dollars per share)	$ 2.69	$ 3.97	$ 6.69	$ 11.92
Granted (in dollars per share)	$ 1.12	$ 3.47	$ 3.76
Vested (in dollars per share)	$ 1.36	$ 11.77	$ 15.03
Forfeited/canceled (in dollars per share)	$ 1.06	$ 4.87	$ 5.80
Ending nonvested restricted stock and units at end of period (in dollars per share)	$ 2.69	$ 3.97	$ 6.69	$ 11.92
Vesting period	3 years
Total unrecognized compensation cost related to restricted stock grants	900,000
Unrecognized compensation expected weighted-average recognition period (in years)	1 year 4 months 24 days
Vesting period	3 years
Restricted Stock [Member] | Outside Director [Member]
Restricted Stock and Units - Weighted Average Stock Grant Price [Abstract]
Vesting period	1 year
Vesting period	1 year
Stock Options [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock based compensation expense	932,000	769,000	13,000
Restricted Stock and Units - Weighted Average Stock Grant Price [Abstract]
Vesting period	4 years
Total unrecognized compensation cost related to restricted stock grants	1,600,000
Options expiration period (in years)	7 years
Vesting period	4 years
Stock Options Shares [Abstract]
Opening stock options outstanding (in shares)	1,252,000	157,000	82,000
Granted (in shares)	43,000	1,269,000	480,000
Exercised (in shares)	0	(1,000)	0
Forfeited/canceled (in shares)	(22,000)	(173,000)	(405,000)
Ending stock options outstanding as of end of period (in shares)	1,273,000	1,252,000	157,000
Ending stock options exercisable (in shares)	240,000	16,000	38,000
Stock Options - Weighted Average Option Grant Price [Abstract]
Opening stock options outstanding (in dollars per share)	$ 4.64	$ 7.41	$ 17.53
Granted (in dollars per share)	$ 0.73	$ 4.66	$ 4.97
Exercised (in dollars per share)	$ 0	$ 3.72	$ 0
Forfeited/canceled (in dollars per share)	$ 4.83	$ 7.25	$ 6.58
Ending stock options outstanding (in dollars per share)	$ 4.51	$ 4.64	$ 7.41
Ending stock options exercisable (in dollars per share)	$ 4.37	$ 4.75	$ 16.55
Stock Options -Aggregate Intrinsic Value [Abstract]
Outstanding as of end of period	0	20,000	0
Exercisable at end of period	0	0	0
Weighted average fair value of stock options granted (in dollars per share)	$ 0.73
Weighted average assumptions based on date of grant [Abstract]
Dividend yield (in hundredths)	1.40%	1.40%	2.00%
Volatility (in hundredths)	80.40%	80.40%	76.60%
Risk-free interest rate (in hundredths)	1.70%	1.70%	2.10%
Expected life (in years)	4 years 9 months 18 days	4 years 9 months 18 days	4 years 9 months 18 days
Exercise prices of the options outstanding, minimum (in dollars per share)	$ 0.73
Exercise prices of the options outstanding, maximum (in dollars per share)	$ 6.15
Selling, General and Administrative Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock based compensation expense	$ 1,889,000	$ 1,639,000	$ 1,846,000