Schedule II - Valuation and Qualifying Accounts (Details) (Allowance for doubtful accounts, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 02, 2011
Allowance for doubtful accounts
Valuation and Qualifying Accounts
Balance at Beginning of Period	$ 2,549		$ 2,546	$ 2,426
Charged to Cost and Expenses	985	1,136	760
Charged to Other Accounts	0	0	0
Deductions, Actual Charge-Offs	(219)	(1,133)	(639)
Balance at End of Period	$ 3,315	$ 2,549		$ 2,426