Quarterly Financial Information (Unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]
Net Sales	$ 326,770,000	$ 288,622,000	$ 286,974,000	$ 269,499,000	$ 260,349,000	$ 268,248,000	$ 280,256,000	$ 290,707,000	$ 1,171,864,171	$ 1,099,559,521	$ 1,023,762,049
Gross Profit	128,694,000	105,962,000	102,613,000	93,464,000	89,119,000	90,116,000	92,757,000	100,826,000	430,732,902	372,818,559	361,580,335
Operating Income	95,636,000	73,656,000	71,596,000	63,854,000	53,819,000	57,623,000	57,512,000	65,501,000	304,741,813	234,455,232	231,367,925
Net Income	$ 69,881,000	$ 55,521,000	$ 52,097,000	$ 45,431,000	$ 39,599,000	$ 41,877,000	$ 40,767,000	$ 46,345,000	$ 222,929,949	$ 168,586,840	$ 164,668,228
Earnings Per Share (Diluted) (in dollars per share)	$ 0.48	$ 0.38	$ 0.36	$ 0.32	$ 0.28	$ 0.29	$ 0.28	$ 0.32	$ 1.55	$ 1.17	$ 1.14
Earnings Per Share (Basic) (in dollars per share)	$ 0.48	$ 0.39	$ 0.36	$ 0.32	$ 0.28	$ 0.29	$ 0.28	$ 0.32	$ 1.55	$ 1.18	$ 1.16