CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions		3 Months Ended				12 Months Ended
		Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income		$ 99.9	$ 50.7	$ 174.7	$ 35.7	$ 570.6	$ 355.9	$ 255.4
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization						1,215.6	876.4	615.9
Deferred income taxes						(490.3)	(62.2)	51.2
Share-based compensation expense related to equity incentive plans						170.2	166.4	93.2
Loss on settlement of debt		3.4	1.9	8.3		5.4	12.6	16.0	$ 43.9
Amortization of debt discount						121.7	114.6	106.1
Amortization of debt issuance costs						17.1	16.5	6.6
Losses on equity method investments						0.0	0.2	0.2
Gains on sale of assets						(2.2)	0.0	(5.9)
Losses on write-down of fixed assets						2.7	0.8	0.1
Impairment of intangible assets						2.2	3.1	0.5
Gains on marketable equity securities						(2.5)	0.0	0.0
Impairment of available-for-sale investments						0.0	6.0	15.5
Amortization of premium on available-for-sale investments						0.0	(0.2)	0.3
Changes in operating assets and liabilities, excluding impact of acquisitions:
(Increase) decrease in accounts receivable						(53.3)	238.8	(85.3)
Decrease (increase) in inventories						28.8	341.6	(59.2)
Increase in deferred income on shipments to distributors						0.0	0.0	41.0
Increase (decrease) in accounts payable and accrued liabilities						11.4	(180.7)	(13.9)
Change in other assets and liabilities						(13.1)	(24.2)	14.0
Change in income tax payable						(40.5)	(190.8)	367.9
Net cash provided by operating activities						1,543.8	1,674.8	1,419.6
Cash flows from investing activities:
Purchases of available-for-sale investments						(2.0)	(167.7)	(1,594.8)
Maturities of available-for-sale investments						0.0	78.0	786.7
Sales of available-for-sale investments and marketable equity securities						4.7	1,376.6	0.0
Acquisition of Microsemi, net of cash acquired						0.0	(7,850.6)	0.0
Investments in other assets						(71.5)	(18.6)	(7.1)
Proceeds from sale of assets						3.2	0.2	10.3
Capital expenditures						(67.6)	(228.9)	(206.8)
Net cash used in investing activities						(133.2)	(6,811.0)	(1,011.7)
Cash flows from financing activities:
Payments on settlement of convertible debt						(615.0)	0.0	(73.4)
Proceeds from borrowings on bridge loan facility						611.9	0.0	0.0
Proceeds from issuance of 2023 and 2021 Senior Notes						0.0	1,989.5	0.0
Repayment of debt assumed in Microsemi acquisition						0.0	(2,056.9)	0.0
Deferred financing costs						(8.9)	(72.7)	(1.2)
Payment of cash dividends						(350.1)	(344.4)	(337.5)
Proceeds from sale of common stock						58.8	42.6	42.0
Tax payments related to shares withheld for vested restricted stock units						(68.1)	(71.8)	(44.4)
Capital lease payments						(0.8)
Capital lease payments							(0.8)	(0.8)
Net cash (used in) provided by financing activities						(1,438.2)	4,663.5	(415.3)
Net decrease in cash and cash equivalents						(27.6)	(472.7)	(7.4)
Cash and cash equivalents, and restricted cash at beginning of period			$ 428.6		$ 901.3	428.6	901.3	908.7
Cash and cash equivalents, and restricted cash at end of period		401.0		428.6		401.0	428.6	901.3	$ 908.7
Supplemental disclosure of cash flow information
Restricted cash		$ 25.0		$ 38.4		25.0	38.4	42.1
Non-cash activities:
Right-of-use assets obtained in exchange of lease liabilities	[1]					24.8
Cash paid for:
Interest						355.2	347.9	85.3
Income taxes						101.3	77.6	25.9
Operating lease payments in operating cash flows	[1]					46.5
Term Loan Facility
Cash flows from financing activities:
Proceeds from borrowings on loan facility						0.0	3,000.0	0.0
Repayments of loan facility						(188.0)	(1,088.5)	0.0
Revolving Credit Facility
Cash flows from financing activities:
Proceeds from borrowings on loan facility						1,026.0	4,416.5	187.0
Repayments of loan facility						$ (1,904.0)	$ (1,150.0)	$ (187.0)

[1] During the fiscal year ended March 31, 2020, the Company adopted Accounting Standards Codification Topic 842, Leases, using the retrospective cumulative effect adjustment transition method. The disclosures are not applicable for the fiscal years ended March 31, 2019 or 2018.