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v3.20.1

Accounts Payable and Accrued Expenses - Additional Information (Detail) $ in Millions | 3 Months Ended
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Mar. 31, 2019 USD ($)
Net decrease in accrued salaries and bonuses | $ 160.5

X
- Definition Increase decrease in accrued salaries and bonuses. + References No definition available. + Details
Name: | md_IncreaseDecreaseInAccruedSalariesAndBonuses
Namespace Prefix: | md_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration