Quarterly Results (unaudited) (Unaudited Operating Data) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Data [Abstract]
Sales	$ 2,099,302		$ 2,220,955		$ 2,176,689		$ 2,096,150		$ 1,949,052		$ 2,080,201		$ 2,035,518		$ 1,901,903		$ 8,593,096	$ 7,966,674	$ 7,216,081
Gross profit	1,114,227		1,170,026		1,127,179		1,097,579		1,027,639		1,089,254		1,058,791		986,959		4,509,011	4,162,643	3,708,901
Operating income	407,710		447,809		425,061		418,626		362,620		415,260		385,768		350,373		1,699,206	1,514,021	1,270,374
Net income	$ 246,030		$ 278,493		$ 257,794		$ 255,374		$ 218,576		$ 266,268		$ 233,508		$ 212,864		$ 1,037,691	$ 931,216	$ 778,182
Earnings per share - basic	$ 2.62	[1]	$ 2.93	[1]	$ 2.69	[1]	$ 2.63	[1]	$ 2.22	[1]	$ 2.68	[1]	$ 2.32	[1]	$ 2.09	[1]	$ 10.87	$ 9.32	$ 7.46
Earnings per share - assuming dilution	$ 2.59	[1]	$ 2.90	[1]	$ 2.65	[1]	$ 2.59	[1]	$ 2.19	[1]	$ 2.64	[1]	$ 2.29	[1]	$ 2.06	[1]	$ 10.73	$ 9.17	$ 7.34

[1] Earnings per share amounts are computed independently for each quarter and annual period. The quarterly earnings per share amounts may not sum to equal the full-year earnings per share amount.