Quarterly financial data (unaudited) (Details) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Feb. 01, 2019 USD ($) item $ / shares	Nov. 02, 2018 USD ($) item $ / shares	Aug. 03, 2018 USD ($) item $ / shares	May 04, 2018 USD ($) item $ / shares	Feb. 02, 2018 USD ($) item $ / shares	Nov. 03, 2017 USD ($) item $ / shares	Aug. 04, 2017 USD ($) item $ / shares	May 05, 2017 USD ($) item $ / shares	Feb. 01, 2019 USD ($) $ / shares	Feb. 02, 2018 USD ($) item $ / shares	Feb. 03, 2017 USD ($) $ / shares
Selected unaudited quarterly financial data
Number of weeks in a quarter | item	13	13	13	13	13	13	13	13
Net sales	$ 6,649,809	$ 6,417,462	$ 6,443,309	$ 6,114,463	$ 6,129,431	$ 5,903,606	$ 5,828,305	$ 5,609,625	$ 25,625,043	$ 23,470,967	$ 21,986,598
Gross profit	2,071,689	1,895,059	1,974,873	1,862,249	1,965,398	1,766,456	1,790,522	1,698,983	7,803,870	7,221,359	6,782,638
Operating profit	638,503	442,143	545,476	490,184	623,446	417,431	493,146	473,795	2,116,306	2,007,818	2,063,449
Net income	$ 483,241	$ 334,142	$ 407,237	$ 364,852	$ 712,155	$ 252,533	$ 294,783	$ 279,489	$ 1,589,472	$ 1,538,960	$ 1,251,133
Basic earnings per share (in dollars per share) | $ / shares	$ 1.85	$ 1.26	$ 1.53	$ 1.36	$ 2.63	$ 0.93	$ 1.08	$ 1.02	$ 5.99	$ 5.64	$ 4.45
Diluted earnings per share (in dollars per share) | $ / shares	$ 1.84	$ 1.26	$ 1.52	$ 1.36	$ 2.63	$ 0.93	$ 1.08	$ 1.02	$ 5.97	$ 5.63	$ 4.43
Number of stores acquired | item							15
Number of stores under assumed lease obligations | item							300
Number of stores closing | item					35					35
Selling, general and administrative expenses					$ 28,300		$ 7,300
Selling, general and administrative expenses, net of tax					$ 17,600		$ 4,400
Effect of pre-tax asset purchase on earnings per diluted share (in dollars per share) | $ / shares					$ (0.07)		$ (0.02)