Quarterly Results (unaudited) (Unaudited Operating Data) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Results (Unaudited)
Sales	$ 2,828,773	$ 3,207,638	$ 3,091,595	$ 2,476,487	$ 2,482,975	$ 2,666,528	$ 2,589,874	$ 2,410,608	$ 11,604,493	$ 10,149,985	$ 9,536,428
Gross profit	1,472,138	1,680,468	1,637,180	1,295,906	1,324,584	1,422,530	1,368,287	1,279,290	6,085,692	5,394,691	5,039,966
Operating income	534,272	725,013	736,490	423,561	441,503	536,363	498,074	444,786	2,419,336	1,920,726	1,815,184
Net income	$ 392,945	$ 527,252	$ 531,667	$ 300,438	$ 324,916	$ 391,293	$ 353,681	$ 321,152	$ 1,752,302	$ 1,391,042	$ 1,324,487
Earnings per share - basic	$ 5.45	$ 7.13	$ 7.16	$ 4.00	$ 4.29	$ 5.14	$ 4.56	$ 4.09	$ 23.74	$ 18.07	$ 16.27
Earnings per share - assuming dilution	$ 5.40	$ 7.07	$ 7.10	$ 3.97	$ 4.25	$ 5.08	$ 4.51	$ 4.05	$ 23.53	$ 17.88	$ 16.10