Stock-based compensation (Details 2) (USD $)	3 Months Ended	12 Months Ended
	Apr. 02, 2013	Dec. 25, 2012
Fixed Options, Shares
Outstanding at the beginning of the period (in shares)	1,074,470
Granted (in shares)	30,000
Exercised (in shares)	(2,831)
Forfeited (in shares)	(77,261)
Outstanding at the end of the period (in shares)	1,024,378	1,074,470
Exercisable at the end of the period (in shares)	684,353	698,372
Weighted-average fair value of options granted during period (in dollars per share)		$ 1.79
Fixed Options, Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 2.34
Granted (in dollars per share)	$ 2.10
Exercised (in dollars per share)	$ 1.18
Forfeited (in dollars per share)	$ 2.67
Outstanding at the end of the period (in dollars per share)	$ 2.31	$ 2.34
Exercisable at the end of the period (in dollars per share)	$ 2.33	$ 2.38
Fixed Options, Weighted Average Remaining Contractual Life
Granted	9 years 9 months 18 days
Outstanding	7 years 1 month 6 days	6 years 10 months 24 days
Exercisable at the end of the period	6 years 4 months 24 days	6 years 2 months 12 days
Fixed Options, Aggregate Intrinsic Value
Outstanding at the beginning of the period (in dollars)	$ 142,536
Outstanding at the end of the period (in dollars)	133,495	142,536
Exercisable at the end of the period (in dollars)	$ 104,036	$ 103,673