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General - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015 Acquisition	Dec. 31, 2014 Acquisition Business
Business Acquisition [Line Items]
Number of complementary business acquired | Acquisition	12	13
Complementary Business [Member]
Business Acquisition [Line Items]
Number of complementary business acquired | Business		2

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The number of businesses acquired by the entity during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfBusinessesAcquired
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_BusinessAcquisitionAxis=md_ComplementaryBusinessMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: