CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net income	$ 349,400,000	$ 570,600,000	$ 355,900,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,153,300,000	1,215,600,000	876,400,000
Deferred income taxes	(138,900,000)	(490,300,000)	(62,200,000)
Share-based compensation expense related to equity incentive plans	198,300,000	170,200,000	166,400,000
Loss on settlement of debt	299,600,000	5,400,000	12,600,000
Amortization of debt discount	71,100,000	121,700,000	114,600,000
Amortization of debt issuance costs	17,100,000	17,100,000	16,500,000
Losses on equity method investments	0	0	200,000
Gains on sale of assets	(7,100,000)	(2,200,000)	0
Losses on write-down of fixed assets	900,000	2,700,000	800,000
Impairment of intangible assets	0	2,200,000	3,100,000
Gains on equity investments	(200,000)	(2,500,000)	0
Impairment of available-for-sale investments	0	0	6,000,000.0
Amortization of premium on available-for-sale investments	0	0	(200,000)
Changes in operating assets and liabilities, excluding impact of acquisitions:
(Increase) decrease in accounts receivable	(63,700,000)	(53,300,000)	238,800,000
Decrease in inventories	18,400,000	28,800,000	341,600,000
Increase (decrease) in accounts payable and accrued liabilities	17,600,000	11,400,000	(180,700,000)
Change in other assets and liabilities	(16,700,000)	(13,100,000)	(24,200,000)
Change in income tax payable	17,400,000	(40,500,000)	(190,800,000)
Net cash provided by operating activities	1,916,500,000	1,543,800,000	1,674,800,000
Cash flows from investing activities:
Purchases of available-for-sale investments	0	(2,000,000.0)	(167,700,000)
Maturities of available-for-sale investments	0	0	78,000,000.0
Sales of available-for-sale investments and marketable equity securities	0	4,700,000	1,376,600,000
Acquisition of Microsemi, net of cash acquired	0	0	(7,850,600,000)
Investments in other assets	(89,000,000.0)	(71,500,000)	(18,600,000)
Proceeds from sale of assets	8,300,000	3,200,000	200,000
Capital expenditures	(92,600,000)	(67,600,000)	(228,900,000)
Net cash used in investing activities	(173,300,000)	(133,200,000)	(6,811,000,000.0)
Cash flows from financing activities:
Proceeds from issuance of senior notes	3,577,800,000	0	1,989,500,000
Proceeds from borrowings on bridge loan facility	0	611,900,000	0
Repayment of bridge loan facility	(615,000,000.0)	0	0
Payments on settlement of convertible debt	(2,611,400,000)	(615,000,000.0)	0
Repayment of debt assumed in Microsemi acquisition	0	0	(2,056,900,000)
Deferred financing costs	(21,200,000)	(8,900,000)	(72,700,000)
Purchase of capped call options	(35,800,000)	0	0
Payment of cash dividends	(388,300,000)	(350,100,000)	(344,400,000)
Proceeds from sale of common stock	60,300,000	58,800,000	42,600,000
Tax payments related to shares withheld for vested restricted stock units	(64,600,000)	(68,100,000)	(71,800,000)
Capital lease payments	(600,000)	(800,000)	(800,000)
Net cash (used in) provided by financing activities	(1,864,200,000)	(1,438,200,000)	4,663,500,000
Net decrease in cash and cash equivalents	(121,000,000.0)	(27,600,000)	(472,700,000)
Cash and cash equivalents, and restricted cash at beginning of period	401,000,000.0	428,600,000	901,300,000
Cash and cash equivalents, and restricted cash at end of period	280,000,000.0	401,000,000.0	428,600,000
Supplemental disclosure of cash flow information:
Restricted cash	0	25,000,000.0	38,400,000
ROU assets obtained in exchange of lease liabilities	65,600,000	24,800,000
Cash paid for interest	265,400,000	355,200,000	347,900,000
Cash paid for income taxes	87,300,000	101,300,000	77,600,000
Operating lease payments in operating cash flows	47,400,000	46,500,000
Revolving Credit Facility
Cash flows from financing activities:
Proceeds from borrowings under line of credit	3,966,000,000.0	1,026,000,000.0	4,416,500,000
Repayments of line of credit	(4,007,900,000)	(1,904,000,000.0)	(1,150,000,000.0)
Term Loan Facility
Cash flows from financing activities:
Proceeds from borrowings under line of credit	0	0	3,000,000,000.0
Repayments of line of credit	$ (1,723,500,000)	$ (188,000,000.0)	$ (1,088,500,000)