SEGMENT REPORTING (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 reportingUnit	Dec. 31, 2020 reportingUnits	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments				2	2
Net sales	$ 6,720,000	$ 6,461,000	$ 17,858,000			$ 18,725,000
Income before income taxes	233,000	145,000	454,000			113,000
Intangible amortization	16,000	16,000	47,000			49,000
Stock-based compensation	25,000	19,000	62,000			53,000
Restructuring charges	30,000	14,600	75,000			199,100
Interest and other, net	7,000	50,000	58,000			153,000
Flex Agility Solutions
Segment Reporting Information [Line Items]
Net sales	3,834,000	3,631,000	10,063,000			11,122,000
Flex Reliability Solutions
Segment Reporting Information [Line Items]
Net sales	2,886,000	2,830,000	7,795,000			7,603,000
Operating Segments
Segment Reporting Information [Line Items]
Net sales	6,720,000	6,461,000	17,858,000			18,725,000
Income before income taxes	311,000	256,000	721,000			691,000
Operating Segments | Flex Agility Solutions
Segment Reporting Information [Line Items]
Net sales	3,834,000	3,631,000	10,063,000			11,122,000
Income before income taxes	153,000	98,000	313,000			301,000
Operating Segments | Flex Reliability Solutions
Segment Reporting Information [Line Items]
Net sales	2,886,000	2,830,000	7,795,000			7,603,000
Income before income taxes	178,000	186,000	472,000			475,000
Operating Segments | Corporate and Other
Segment Reporting Information [Line Items]
Income before income taxes	(20,000)	(28,000)	(64,000)			(85,000)
Segment Reconciling Items
Segment Reporting Information [Line Items]
Intangible amortization	16,000	16,000	47,000			49,000
Stock-based compensation	25,000	19,000	62,000			53,000
Customer related asset impairments (recoveries)	0	4,000	(3,000)			95,000
Restructuring charges	30,000	15,000	75,000			199,000
Legal and other	0	7,000	28,000			29,000
Interest and other, net	$ 7,000	$ 50,000	$ 58,000			$ 153,000