Subsequent Event (Details) (USD $) In Billions, except Per Share data, unless otherwise specified	Jul. 20, 2011
Subsequent Event (Textuals) [Abstract]
Total consideration for Medco shareholders	$ 29.1
Cash and stock paid per share for Medco shareholders	$ 71.36
Cash paid per share for Medco shareholders	$ 28.80
Stock paid per share for Medco shareholders	$ 0.81
Express Scripts, Inc. [Member]
Business Acquisition [Line Items]
Percentage of voting rights company owned	59.00%
Medco [Member]
Business Acquisition [Line Items]
Percentage of voting rights company owned	41.00%

Business Acquisition Cost Of Acquired Entity Cash Paid Per Share.

Name:	esrx_BusinessAcquisitionCostOfAcquiredEntityCashAndStockPaidPerShare
Namespace Prefix:	esrx
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Business Acquisition Purchase Consideration Payable In Cash Per Share.

+ Details

Name:	esrx_BusinessAcquisitionPurchaseConsiderationPayableInCashPerShare
Namespace Prefix:	esrx
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Business Acquisition Purchase Consideration Payable In Stock Per Share.

+ Details

Name:	esrx_BusinessAcquisitionPurchaseConsiderationPayableInStockPerShare
Namespace Prefix:	esrx
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Subsequent event.

+ Details

Name:	esrx_SubsequentEventTextualsAbstract
Namespace Prefix:	esrx
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The total cost of the acquired entity including the cash paid to shareholders of acquired entities, fair value of debt and equity securities issued to shareholders of acquired entities, the fair value of the liabilities assumed, and direct costs of the acquisition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 51
-Subparagraph d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_BusinessAcquisitionCostOfAcquiredEntityPurchasePrice
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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.

+ Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of voting equity interests acquired in the business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141R
-Paragraph 68
-Subparagraph c
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6909870&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix:	us-gaap
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant