Quarterly Financial Data - Summary of Quarterly Financial Data (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2012	Oct. 31, 2011	Jul. 31, 2011	Apr. 30, 2011	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Schedule Of Quarterly Financial Data [Line Items]
Net sales	$ 1,235,769	$ 852,741	$ 886,569	$ 819,170	$ 1,187,440	$ 821,767	$ 872,712	$ 761,018	$ 3,794,249	$ 3,642,937	$ 3,085,290
Gross profit	730,815	464,289	499,162	469,018	716,915	475,849	514,697	443,693	2,163,284	2,151,154	1,822,278
Earnings from operations	290,357	117,295	154,580	134,985	285,743	146,177	140,540	135,966	697,217	708,426	594,781
Net earnings	$ 179,643	$ 63,179	$ 91,801	$ 81,534	$ 178,395	$ 89,689	$ 90,043	$ 81,063	$ 416,157	$ 439,190	$ 368,403
Basic	$ 1.42	$ 0.50	$ 0.72	$ 0.64	$ 1.41	$ 0.71	$ 0.70	$ 0.64	$ 3.28	$ 3.45	$ 2.91
Diluted	$ 1.40	$ 0.49	$ 0.72	$ 0.64	$ 1.39	$ 0.70	$ 0.69	$ 0.63	$ 3.25	$ 3.40	$ 2.87