Quarterly Results (unaudited) (Unaudited Operating Data) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Data [Abstract]
Sales	$ 1,764,178		$ 1,876,872		$ 1,847,088		$ 1,727,943		$ 1,621,234		$ 1,728,025		$ 1,714,969		$ 1,585,009		$ 7,216,081	$ 6,649,237	$ 6,182,184
Gross profit	912,107		968,201		950,877		877,716		819,300		879,163		871,875		798,663		3,708,901	3,369,001	3,097,418
Operating income	303,012		343,768		336,474		287,120		255,760		300,380		296,261		251,084		1,270,374	1,103,485	977,393
Net income	$ 181,678		$ 216,997		$ 205,647		$ 173,860		$ 152,347		$ 186,489		$ 177,127		$ 154,329		$ 778,182	$ 670,292	$ 585,746
Earnings per share - basic	$ 1.79	[1]	$ 2.10	[1]	$ 1.94	[1]	$ 1.64	[1]	$ 1.43	[1]	$ 1.72	[1]	$ 1.61	[1]	$ 1.38	[1]	$ 7.46	$ 6.14	$ 4.83
Earnings per share - assuming dilution	$ 1.76	[1]	$ 2.06	[1]	$ 1.91	[1]	$ 1.61	[1]	$ 1.40	[1]	$ 1.69	[1]	$ 1.58	[1]	$ 1.36	[1]	$ 7.34	$ 6.03	$ 4.75

[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.