Consolidated Condensed Statements of Comprehensive Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net sales	$ 212,820	$ 197,154	$ 414,884	$ 383,720
Cost of sales	96,549	92,502	189,056	179,183
Gross profit	116,271	104,652	225,828	204,537
Selling and administrative expense	89,604	83,828	174,172	178,589
Research and development expense	9,985	8,041	17,696	15,659
Operating expenses	99,589	91,869	191,868	194,248
Income from operations	16,682	12,783	33,960	10,289
Interest expense	5,091	4,398	9,909	8,518
Income before income taxes	11,591	8,385	24,051	1,771
Provision for income taxes	2,872	2,246	4,675	177
Net income	8,719	6,139	19,376	1,594
Comprehensive income	$ 7,307	$ 10,144	$ 20,709	$ 9,220
Per share data:
Basic (in dollars per share)	$ 0.31	$ 0.22	$ 0.69	$ 0.06
Diluted (in dollars per share)	0.30	0.22	0.67	0.06
Dividends per share of common stock (in dollars per share)	$ 0.20	$ 0.20	$ 0.40	$ 0.40
Weighted average common shares:
Basic (shares)	28,075	27,891	28,059	27,894
Diluted (shares)	28,846	28,139	28,739	28,086