SEGMENT AND GEOGRAPHIC INFORMATION (Details) - USD ($) $ 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
Segment Reporting Information
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
Operating income (loss)									106,989	110,795	90,361
Total assets	1,185,353				1,039,905				1,185,353	1,039,905	996,100
Depreciation									29,900	27,100	26,800
Amortization									8,600	8,400	8,600
Capital expenditures									33,400	37,600	25,900
Long-lived assets	587,300				551,500				587,300	551,500	554,800
Water Systems
Segment Reporting Information
Net sales									703,300	723,200	707,600
Distribution
Segment Reporting Information
Net sales									176,700	0	0
Fueling Systems
Segment Reporting Information
Net sales									244,900	226,700	217,300
United States
Segment Reporting Information
Net sales									596,600	446,900	418,500
Long-lived assets	326,100				349,200				326,100	349,200	404,100
Foreign
Segment Reporting Information
Net sales									528,300	503,000	506,400
Long-lived assets	261,200				202,300				261,200	202,300	150,700
Operating Segments | Water Systems
Segment Reporting Information
Net sales									748,600	723,200	707,600
Operating income (loss)									102,000	108,200	86,700
Total assets	695,400				671,500				695,400	671,500	677,600
Depreciation									20,900	19,500	19,500
Amortization									6,200	6,400	6,600
Capital expenditures									19,100	31,800	19,500
Operating Segments | Distribution
Segment Reporting Information
Net sales									176,700	0	0
Operating income (loss)									3,700	0	0
Total assets	153,100				0				153,100	0	0
Depreciation									1,300	0	0
Amortization									400	0	0
Capital expenditures									1,100	0	0
Operating Segments | Fueling Systems
Segment Reporting Information
Net sales									245,900	226,700	217,300
Operating income (loss)									60,000	56,300	51,500
Total assets	265,700				251,100				265,700	251,100	248,500
Depreciation									2,200	2,300	2,500
Amortization									1,900	1,900	1,900
Capital expenditures									11,000	2,100	1,400
Intersegment Sales | Water Systems
Segment Reporting Information
Net sales									45,300	0	0
Intersegment Sales | Distribution
Segment Reporting Information
Net sales									0	0	0
Intersegment Sales | Fueling Systems
Segment Reporting Information
Net sales									1,000	0	0
Intersegment Eliminations/Other
Segment Reporting Information
Net sales									(46,300)	0	0
Operating income (loss)									(58,700)	(53,700)	(47,800)
Total assets					$ 117,300					117,300	70,000
Depreciation									5,500	5,300	4,800
Amortization									100	100	100
Capital expenditures									2,200	$ 3,700	$ 5,000
Intersegment Eliminations/Other | Intersegment Eliminations/Other
Segment Reporting Information
Total assets	$ 71,200								$ 71,200