CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Net sales		$ 1,374.7	$ 994.2	$ 4,019.7	$ 2,978.5
Cost of sales	[1]	595.1	387.1	1,908.8	1,172.9
Gross profit		779.6	607.1	2,110.9	1,805.6
Research and development	[1]	217.7	131.6	611.6	395.7
Selling, general and administrative	[1]	174.8	109.1	515.5	337.6
Amortization of acquired intangible assets		193.7	121.0	497.2	362.8
Special charges and other, net	[1]	(1.3)	0.2	57.0	17.3
Operating expenses		584.9	361.9	1,681.3	1,113.4
Operating income		194.7	245.2	429.6	692.2
Losses on equity method investment		(0.1)	(0.1)	(0.2)	(0.2)
Other income (expense):
Interest income		0.7	6.3	7.3	14.4
Interest expense		(137.6)	(49.7)	(366.7)	(148.7)
Loss on settlement of debt		(0.2)	(2.1)	(4.3)	(16.0)
Other (loss) income, net		(2.5)	(2.9)	(12.4)	7.4
Income before income taxes		55.0	196.7	53.3	549.1
Income tax (benefit) provision		5.8	447.8	(127.9)	440.4
Net income (loss)		$ 49.2	$ (251.1)	$ 181.2	$ 108.7
Basic net income attributable to Microchip Technology, per common share (in usd per share)		$ 0.21	$ (1.07)	$ 0.77	$ 0.47
Diluted net income attributable to Microchip Technology, per common share (in usd per share)		0.20	(1.07)	0.73	0.44
Dividends declared per common share (in usd per share)		$ 0.3645	$ 0.3625	$ 1.092	$ 1.086
Basic common shares outstanding (in shares)		236.7	234.1	235.9	232.3
Diluted common shares outstanding (in shares)		244.6	234.1	249.5	248.0

[1] Includes share-based compensation expense as follows: Cost of sales$3.4 $3.5 $10.9 $10.6Research and development$19.4 $10.9 $53.2 $31.8Selling, general and administrative$16.6 $9.6 $46.1 $27.6Special (income) charges and other, net$0.2 $— $17.3 $—