Receivables, net (Details) (USD $) In Thousands, unless otherwise specified	Sep. 27, 2014	Dec. 28, 2013
Current and long-term receivables balances
Accounts receivable	$ 77,311	$ 76,057
Unbilled accounts receivable	30,323	31,567
Long-term receivables	4,957	3,672
Total receivables	112,591	111,296
Less allowance for doubtful accounts	0	0
Total receivables, net	$ 112,591	$ 111,296