CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 532,357	$ 422,599	$ 437,120
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	177,351	165,834	142,958
(Gain) / loss on disposition of property and equipment	(567)	460	579
Share-based compensation expense	28,921	29,202	23,554
Deferred income taxes	11,887	26,724	9,976
Change in assets and liabilities
Inventories	(136,334)	(83,552)	(67,650)
Prepaid expenses and other current assets	(26,195)	2,305	1,782
Accounts payable	43,413	57,046	82,477
Accrued employee compensation	22,373	6,427	(18,237)
Other accrued expenses	36,406	(10,338)	20,368
Income taxes	(8,355)	4,210	11,787
Other	13,137	10,533	5,997
Net cash provided by operating activities	694,394	631,450	650,711
Cash flows from investing activities:
Capital expenditures	(278,530)	(250,401)	(226,017)
Proceeds from sale of property and equipment	2,216	11,220	362
Acquisition of Petsense, net of cash acquired	0	1,225	(143,610)
Net cash used in investing activities	(276,314)	(237,956)	(369,265)
Cash flows from financing activities:
Borrowings under debt facilities	1,193,500	1,180,000	945,000
Repayments under debt facilities	(1,212,250)	(1,027,500)	(820,000)
Debt issuance costs	(346)	(599)	(1,380)
Principal payments under capital lease obligations	(3,246)	(2,446)	(1,150)
Repurchase of shares to satisfy tax obligations	(1,367)	(816)	(843)
Repurchase of common stock	(349,776)	(369,403)	(331,708)
Net proceeds from issuance of common stock	79,643	16,330	41,010
Cash dividends paid to stockholders	(147,087)	(133,828)	(122,272)
Net cash used in financing activities	(440,929)	(338,262)	(291,343)
Net change in cash and cash equivalents	(22,849)	55,232	(9,897)
Cash and cash equivalents at beginning of year	109,148	53,916	63,813
Cash and cash equivalents at end of year	86,299	109,148	53,916
Cash paid during the year for:
Interest	18,069	10,481	6,124
Income taxes	146,918	219,081	232,258
Supplemental disclosures of non-cash activities [Abstract]
Property and equipment acquired through capital lease	0	11,395	10,493
Non-cash accruals for construction in progress	$ 3,001	$ 8,647	$ 12,303