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Common Stock Repurchase Programs - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Oct. 31, 2014	Dec. 15, 2014	Dec. 17, 2014
Common Stock [Line Items]
Common stock paid	$ 488.4us-gaap_StockRepurchaseProgramAuthorizedAmount1	$ 600.0us-gaap_StockRepurchaseProgramAuthorizedAmount1
Common stock shares issued	7.1us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
Amount withheld to satisfy minimum statutory tax withholding obligations	1.1us-gaap_RestrictedStockValueSharesIssuedNetOfTaxWithholdings
JPMorgan Chase Bank, N.A [Member]
Common Stock [Line Items]
Common stock purchase			200.0us-gaap_AcceleratedShareRepurchasesSettlementPaymentOrReceipt / dei_LegalEntityAxis = md_JpMorganChaseBankMember
Accelerated Share Repurchase (ASR) Agreements [Member] | JPMorgan Chase Bank, N.A [Member]
Common Stock [Line Items]
Common stock paid				$ 200.0us-gaap_StockRepurchaseProgramAuthorizedAmount1 / dei_LegalEntityAxis = md_JpMorganChaseBankMember / us-gaap_ShareRepurchaseProgramAxis = md_AcceleratedShareRepurchaseAgreementsMember
Common stock shares issued				2.5us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased / dei_LegalEntityAxis = md_JpMorganChaseBankMember / us-gaap_ShareRepurchaseProgramAxis = md_AcceleratedShareRepurchaseAgreementsMember

X

- Details

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Namespace Prefix:	md_
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- Definition

Amount of cash receipt from (payment to) bank; or stock received from (issuance to) bank in the settlement of the accelerated share repurchase agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 30

-Section 25

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6405686&loc=d3e22802-112653

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

The value of restricted shares issued as compensation, net of the value of shares for the payment of withholding taxes. This element is to be used only if shares are used in lieu of cash to satisfy all or a portion of withholding taxes.

+ References

No definition available.

+ Details

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

X

- Definition

Amount of stock repurchase plan authorized.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

+ References

No definition available.

+ Details

Name:	us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
Namespace Prefix:	us-gaap_
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Period Type:	instant

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- Details

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- Details

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