ACQUISITIONS Acquisitions (Pro Forma Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Oct. 01, 2016	Jul. 02, 2016	Apr. 02, 2016	Dec. 31, 2017	Dec. 31, 2016	Jan. 02, 2016
Business Combinations [Abstract]
Net sales	$ 288,200	$ 311,100	$ 305,300	$ 220,300	$ 239,600	$ 239,800	$ 252,100	$ 218,400	$ 1,124,909	$ 949,856	$ 924,923
Business Acquisition, Pro Forma Revenue									1,184,800	1,144,600
Net Income Attributable to Franklin Electric Co., Inc.	$ 8,100	$ 24,500	$ 29,900	$ 15,700	$ 17,500	$ 23,700	$ 24,000	$ 13,500	78,180	78,745	$ 72,945
Business Acquisition, Pro Forma Net Income (Loss)									$ 79,400	$ 85,000
Earnings Per Share, Basic	$ 0.17	$ 0.52	$ 0.64	$ 0.33	$ 0.37	$ 0.51	$ 0.51	$ 0.28	$ 1.67	$ 1.67	$ 1.52
Business Acquisition, Pro Forma Earnings Per Share, Basic									1.70	1.80
Earnings Per Share, Diluted	$ 0.17	$ 0.52	$ 0.64	$ 0.33	$ 0.37	$ 0.50	$ 0.50	$ 0.28	1.65	1.65	$ 1.50
Business Acquisition, Pro Forma Earnings Per Share, Diluted									$ 1.68	$ 1.78
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual	$ 176,700
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual	$ 1,400