Financial Instruments (Details) (Recurring [Member], USD $) In Thousands, unless otherwise specified	Apr. 01, 2012	Jan. 01, 2012
Carrying value and estimated fair value of financial instruments
Interest rate swap derivative assets	$ 7,258	$ 7,440
Restricted investments:
Guaranteed Investment Contract	5,742	5,742
Guaranteed Repurchase Agreements	35,656	33,821
Rabbi Trust	8,711	8,016
Fixed income securities	2,048	2,013
Quoted Prices in Active Markets (Level 1) [Member]
Carrying value and estimated fair value of financial instruments
Interest rate swap derivative assets	0	0
Restricted investments:
Guaranteed Investment Contract	0	0
Guaranteed Repurchase Agreements	0	0
Rabbi Trust	6,585	5,898
Fixed income securities	0	0
Significant Other Observable Inputs (Level 2) [Member]
Carrying value and estimated fair value of financial instruments
Interest rate swap derivative assets	7,258	7,440
Restricted investments:
Guaranteed Investment Contract	5,742	5,742
Guaranteed Repurchase Agreements	35,656	33,821
Rabbi Trust	2,126	2,118
Fixed income securities	2,048	2,013
Significant Unobservable Inputs (Level 3) [Member]
Carrying value and estimated fair value of financial instruments
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