Financial Instruments (Details) (Recurring [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Jan. 01, 2012
Assets:
Interest rate swap derivative assets	$ 6,212	$ 7,440
Restricted investments:
Guaranteed Investment Contract	5,742	5,742
Guaranteed Repurchase Agreements	0	33,821
Rabbi Trust	7,718	8,016
Fixed income securities	2,152	2,013
Liabilities:
Interest rate swap derivative liability	708
Quoted Prices in Active Markets (Level 1) [Member]
Assets:
Interest rate swap derivative assets	0	0
Restricted investments:
Guaranteed Investment Contract	0	0
Guaranteed Repurchase Agreements	0	0
Rabbi Trust	7,718	5,898
Fixed income securities	0	0
Liabilities:
Interest rate swap derivative liability	0
Significant Other Observable Inputs (Level 2) [Member]
Assets:
Interest rate swap derivative assets	6,212	7,440
Restricted investments:
Guaranteed Investment Contract	5,742	5,742
Guaranteed Repurchase Agreements	0	33,821
Rabbi Trust	0	2,118
Fixed income securities	2,152	2,013
Liabilities:
Interest rate swap derivative liability	708
Significant Unobservable Inputs (Level 3) [Member]
Assets:
Interest rate swap derivative assets	0	0
Restricted investments:
Guaranteed Investment Contract	0	0
Guaranteed Repurchase Agreements	0	0
Rabbi Trust	0	0
Fixed income securities	0	0
Liabilities:
Interest rate swap derivative liability	$ 0