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Financial Instruments (Narrative) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Financial Instruments [Line Items]
Realized loss or gains	$ 0	$ 0
US Treasury and Government Short-term Debt Securities [Member]
Financial Instruments [Line Items]
Available for Sale Securities Maturity Period	2 years

X

- Definition

Number of maturity year relating to investment securities.

+ References

No definition available.

+ Details

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Namespace Prefix:	med_
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X

- References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of realized gain (loss) on investment in debt and equity securities.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

X

- Details

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Balance Type:
Period Type: