BUSINESS SEGMENTS - Segment Information (Detail) - USD ($) $ in Millions		3 Months Ended																12 Months Ended
		Jan. 03, 2020		Sep. 27, 2019	[2]	Jun. 28, 2019	[3]	Mar. 29, 2019	[4]	Dec. 28, 2018		Sep. 28, 2018	[6]	Jun. 29, 2018	[7]	Mar. 30, 2018	[8]	Jan. 03, 2020	Dec. 28, 2018	Dec. 29, 2017
Segment Reporting Information [Line Items]
Net sales		$ 2,252.3	[1]	$ 2,222.2		$ 2,262.6		$ 2,108.5		$ 2,119.1	[5]	$ 2,179.0		$ 2,137.9		$ 1,964.2		$ 8,845.6	$ 8,400.2	$ 7,927.4
Operating income (loss)		(85.4)	[1]	$ (101.8)		$ (105.7)		$ (74.6)		(87.3)	[5]	$ (89.5)		$ (71.3)		$ (61.6)		(367.5)	(309.7)	(312.9)
Depreciation																		37.2	31.7	28.2
Amortization of intangible assets																		35.0	37.3	36.1
Total assets		4,808.9								4,653.1								4,808.9	4,653.1
Capital expenditures																		40.0	42.4	41.1
Network and Security Solutions [Member]
Segment Reporting Information [Line Items]
Net sales																		4,696.2	4,347.0	4,114.4
Operating income (loss)																		(325.5)	(272.2)	(262.6)
Depreciation																		9.4	3.8	3.1
Amortization of intangible assets																		16.4	17.0	14.4
Total assets		2,224.8								2,319.3								2,224.8	2,319.3	1,947.1
Capital expenditures																		3.1	8.7	3.7
Electrical and Electronic Solutions [Member]
Segment Reporting Information [Line Items]
Net sales																		2,352.0	2,342.7	2,225.5
Operating income (loss)																		(139.5)	(132.3)	(114.3)
Depreciation																		7.3	2.4	2.4
Amortization of intangible assets																		5.4	7.0	8.4
Total assets		1,085.2								1,097.4								1,085.2	1,097.4	1,068.3
Capital expenditures																		1.7	2.0	1.9
Utility Power Solutions [Member]
Segment Reporting Information [Line Items]
Net sales																		1,797.4	1,710.5	1,587.5
Operating income (loss)																		(83.5)	(75.4)	(73.1)
Depreciation																		3.7	3.6	3.9
Amortization of intangible assets																		13.2	13.3	13.3
Total assets		943.6								905.5								943.6	905.5	871.4
Capital expenditures																		14.6	6.7	1.7
Corporate [Member]
Segment Reporting Information [Line Items]
Net sales	[9]																	0.0	0.0	0.0
Operating income (loss)	[9]																	181.0	170.2	137.1
Depreciation	[9]																	16.8	21.9	18.8
Amortization of intangible assets	[9]																	0.0	0.0	0.0
Total assets	[9]	555.2								330.9								555.2	330.9	365.4
Capital expenditures	[9]																	20.6	25.0	33.8
Continuing Operations [Member]
Segment Reporting Information [Line Items]
Net sales																		8,845.6	8,400.2	7,927.4
Operating income (loss)																		(367.5)	(309.7)	(312.9)
Depreciation																		37.2	31.7	28.2
Amortization of intangible assets																		35.0	37.3	36.1
Total assets		$ 4,808.9								$ 4,653.1								4,808.9	4,653.1	4,252.2
Capital expenditures																		$ 40.0	$ 42.4	$ 41.1

[1] In the fourth quarter of 2019, "Operating income" includes $8.6 million of intangible asset amortization and $12.8 million of merger costs. "Net income" includes a $45.9 million tax benefit related to the reversal of deferred income tax valuation allowances, partially offset by $0.8 million of tax expense related to prior year tax positions.

[2] In the third quarter of 2019, "Operating income" includes $8.8 million of intangible asset amortization.

[3] In the second quarter of 2019, "Operating income" includes $8.8 million of intangible asset amortization.

[4] In the first quarter of 2019, "Operating income" includes $8.8 million of intangible asset amortization and a reversal of acquisition and integration costs of $0.3 million.

[5] In the fourth quarter of 2018, "Operating income" includes $8.7 million of intangible asset amortization and $0.2 million of U.K. facility relocation costs. "Income before income taxes" includes a $4.6 million loss on extinguishment of debt.

[6] In the third quarter of 2018, "Operating income" includes $9.6 million of intangible asset amortization, a restructuring charge of $0.2 million, $0.3 million of acquisition and integration costs and $0.2 million of U.K. facility relocation costs.

[7] In the second quarter of 2018, "Operating income" includes $9.7 million of intangible asset amortization, a restructuring charge of $9.2 million, $2.3 million of acquisition and integration costs, $2.6 million of CEO retirement agreement expense and $0.4 million of U.K. facility relocation costs.

[8] In the first quarter of 2018, "Operating income" includes $9.3 million of intangible asset amortization, $0.3 million of acquisition and integration costs and $0.2 million of U.K. facility relocation costs.

[9] Corporate "Total assets" primarily consists of cash and cash equivalents, deferred tax assets, and corporate fixed assets. Total assets in 2019 include the impact of the Company's adoption of ASU 2016-02, Leases, which resulted in the recognition of right-of-use assets for all leases with terms of more than 12 months.