Selected Quarterly Financial Data (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jul. 01, 2012	Apr. 01, 2012	Jan. 01, 2012	Oct. 02, 2011	Jul. 03, 2011	Apr. 03, 2011	Dec. 31, 2012	Jan. 01, 2012	Jan. 02, 2011
Company's quarterly financial data
Revenues	$ 378,731	$ 369,115	$ 371,174	$ 360,042	$ 354,473	$ 354,728	$ 356,012	$ 341,959	$ 1,479,062	$ 1,407,172	$ 1,084,592
Operating Income	39,313	51,602	52,941	40,497	47,298	47,265	46,298	38,738	184,353	179,599	126,902
Net Income	95,413	14,532	20,858	13,755	17,176	18,820	18,620	15,028	144,558	69,644	54,371
Net income loss from discontinued operations	$ (13,777)	$ 194	$ 1,619	$ 1,304	$ 1,450	$ 2,474	$ 2,544	$ 1,351	$ (10,660)	$ 7,819	$ 8,419
Basic earnings per share
Income from continuing operations	$ 1.56	$ 0.25	$ 0.34	$ 0.23	$ 0.28	$ 0.30	$ 0.30	$ 0.24	$ 2.39	$ 1.12	$ 0.99
Income (loss) from discontinued operations	$ (0.23)	$ 0.00	$ 0.03	$ 0.02	$ 0.02	$ 0.04	$ 0.04	$ 0.02	$ (0.17)	$ 0.12	$ 0.15
Net income per share — basic	$ 1.33	$ 0.26	$ 0.37	$ 0.25	$ 0.30	$ 0.34	$ 0.33	$ 0.26	$ 2.21	$ 1.24	$ 1.15
Diluted:
Income from continuing operations	$ 1.55	$ 0.25	$ 0.34	$ 0.23	$ 0.28	$ 0.30	$ 0.29	$ 0.24	$ 2.37	$ 1.11	$ 0.98
Income from discontinued operations	$ (0.22)	$ 0.00	$ 0.03	$ 0.02	$ 0.02	$ 0.04	$ 0.04	$ 0.02	$ (0.17)	$ 0.12	$ 0.15
Net income per share — diluted	$ 1.32	$ 0.25	$ 0.37	$ 0.25	$ 0.30	$ 0.34	$ 0.33	$ 0.26	$ 2.20	$ 1.23	$ 1.13