Quarterly Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 29, 2015	Sep. 29, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 30, 2014	Sep. 30, 2014	Jul. 01, 2014	Apr. 01, 2014	Dec. 29, 2015	Dec. 30, 2014	Dec. 31, 2013
Quarterly Financial Data (unaudited)
Revenues	$ 526,841	$ 526,688	$ 529,107	$ 517,973	$ 499,673	$ 499,114	$ 496,406	$ 481,431	$ 2,100,609	$ 1,976,624	$ 1,877,910
Income/(loss) from operations	38,795	35,644	49,753	41,054	34,792	34,175	42,691	33,073	165,246	144,731	160,954
Net income	$ 27,200	$ 26,176	$ 34,724	$ 28,423	$ 24,486	$ 24,223	$ 30,049	$ 22,518	$ 116,523	$ 101,276	$ 114,356
Basic net income per share (in dollars per share)	$ 0.56	$ 0.54	$ 0.72	$ 0.58	$ 0.50	$ 0.49	$ 0.61	$ 0.44	$ 2.39	$ 2.04	$ 2.19
Diluted net income per share (in dollars per share)	0.54	0.52	0.69	0.56	0.48	0.48	0.59	0.43	2.30	1.96	2.10
Cash dividends declared per common share (in dollars per share)	$ 0.20	$ 0.20	$ 0.165	$ 0.165	$ 0.165	$ 0.165	$ 0.14	$ 0.14	$ 0.73	$ 0.61	$ 0.52