CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Net sales	$ 3,980.8	$ 3,407.8	$ 2,173.3
Cost of sales	1,560.1	1,650.6	967.8
Gross profit	2,420.7	1,757.2	1,205.5
Operating expenses:
Research and development	529.3	545.3	372.6
Selling, general and administrative	452.1	499.8	301.7
Amortization of acquired intangible assets	485.5	337.7	174.9
Special charges and other, net	17.5	98.6	4.0
Operating expenses	1,484.4	1,481.4	853.2
Operating income	936.3	275.8	352.3
Losses on equity method investments	(0.2)	(0.2)	(0.3)
Other income (expense):
Interest income	22.0	3.1	24.4
Interest expense	(199.0)	(146.3)	(104.0)
Loss on settlement of convertible debt	(16.0)	(43.9)	0.0
Other (loss) income, net	(5.8)	1.3	8.9
Income before income taxes	737.3	89.8	281.3
Income tax provision (benefit)	481.9	(80.8)	(42.6)
Net income from continuing operations	255.4	170.6	323.9
Discontinued operations:
Loss from discontinued operations	0.0	(7.6)	0.0
Income tax benefit	0.0	(1.6)	0.0
Net loss from discontinued operations	0.0	(6.0)	0.0
Net income from continuing operations	255.4	164.6	323.9
Less: Net loss attributable to noncontrolling interests	0.0	0.0	0.2
Net income attributable to Microchip Technology	$ 255.4	$ 164.6	$ 324.1
Basic net income per common share attributable to Microchip Technology stockholders
Net income from continuing operations (in usd per share)	$ 1.10	$ 0.79	$ 1.59
Net loss from discontinued operations (in usd per share)	0.00	(0.03)	0.00
Net income attributable to Microchip Technology (in usd per share)	1.10	0.76	1.59
Diluted net income per common share attributable to Microchip Technology stockholders
Net income from continuing operations (in usd per share)	1.03	0.73	1.49
Net loss from discontinued operations (in usd per share)	0.00	(0.02)	0.00
Net income attributable to Microchip Technology (in usd per share)	1.03	0.71	1.49
Dividends declared per common share	$ 1.449	$ 1.441	$ 1.433
Basic common shares outstanding	232.9	217.2	203.4
Diluted common shares outstanding	248.9	234.8	217.4