Quarterly Financial Information (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Net Sales	$ 443,836,000	$ 477,761,000	$ 468,711,000	$ 468,589,000	$ 453,409,000	$ 460,253,000	$ 454,981,000	$ 465,420,000	$ 1,858,897,406	$ 1,834,063,697	$ 1,794,872,578
Gross Profit	161,805,000	180,321,000	176,538,000	169,645,000	172,044,000	172,990,000	172,804,000	172,628,000	688,307,969	690,466,692	694,528,266
Operating Income	110,901,000	128,136,000	127,905,000	121,596,000	125,499,000	127,428,000	126,683,000	128,515,000	488,537,604	508,125,547	523,358,352
Net income	$ 99,547,000	$ 111,898,000	$ 108,959,000	$ 104,280,000	$ 106,275,000	$ 111,336,000	$ 109,024,000	$ 111,249,000	$ 424,683,939	$ 437,883,097	$ 406,791,922
Earnings Per Share (Basic) (in dollars per share)	$ 0.39	$ 0.44	$ 0.42	$ 0.40	$ 0.41	$ 0.42	$ 0.40	$ 0.40	$ 1.67	$ 1.64	$ 1.42
Earnings Per Share (Diluted) (in dollars per share)	$ 0.39	$ 0.44	$ 0.42	$ 0.40	$ 0.41	$ 0.42	$ 0.40	$ 0.40	$ 1.66	$ 1.62	$ 1.41