EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	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
Numerator:
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
Less: Undistributed earnings allocated to participating securities									600	700	700
Less: Undistributed earnings allocated to redeemable noncontrolling interest									0	1,000	800
Net income available to common shareholders									$ 77,600	$ 77,000	$ 71,400
Denominator:
Basic weighted average common shares outstanding (in shares)									46.5	46.2	47.1
Effect of dilutive securities:
Non-participating employee stock options and performance awards (in shares)									0.5	0.5	0.5
Diluted weighted average common shares outstanding (in shares)									47.0	46.7	47.6
Basic earnings per share (in dollars per share)	$ 0.17	$ 0.52	$ 0.64	$ 0.33	$ 0.37	$ 0.51	$ 0.51	$ 0.28	$ 1.67	$ 1.67	$ 1.52
Diluted earnings per share (in dollars per share)	$ 0.17	$ 0.52	$ 0.64	$ 0.33	$ 0.37	$ 0.50	$ 0.50	$ 0.28	$ 1.65	$ 1.65	$ 1.50
Anti-dilutive stock options (in shares)									0.3	0.4	0.3