Net Income Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income	$ 35.7	$ 170.6
Weighted average common shares outstanding	235.2	229.4
Dilutive effect of stock options and RSUs	4.0	4.5
Weighted average common and potential common shares outstanding	252.2	242.9
Basic net income attributable to Microchip Technology, per common share (in USD per share)	$ 0.15	$ 0.74
Diluted net income attributable to Microchip Technology, per common share (in USD per share)	$ 0.14	$ 0.70
2007 Junior Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities	0.0	4.1
Weighted average conversion price per share used in calculating dilutive effect of convertible debt (amount per share)	$ 0.00	$ 23.69
2015 Senior Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities	13.0		4.9
Weighted average conversion price per share used in calculating dilutive effect of convertible debt (amount per share)	$ 63.27	$ 64.35
2017 Senior Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities	0.0	0.0
Weighted average conversion price per share used in calculating dilutive effect of convertible debt (amount per share)	$ 98.67	$ 100.35
2017 Junior Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities	0.0	0.0
Weighted average conversion price per share used in calculating dilutive effect of convertible debt (amount per share)	$ 96.93	$ 98.59

The weighted average price per share of the conversion feature embedded in the debt instrument.

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