Condensed Consolidating Financial Information (Details 2) (USD $) In Millions	6 Months Ended	12 Months Ended
Jun. 30, 2009	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Condensed Consolidating Statement of Cash Flows
Net cash flows provided by (used in) operating activities		$ 2,117.4	$ 1,771.5	$ 1,103.0
Cash flows from investing activities:
Acquisitions, net of cash acquired, and investment in joint venture			(4,672.6)	(251.5)
Purchase of short-term investments		(38.0)	(1,201.4)
Sale of short-term investments			1,198.9
Purchases of property and equipment		(119.9)	(147.5)	(83.8)
Proceeds from the sale of business		2.5		27.7
Other		12.8	2.1	(11.0)
Net cash used in investing activities - continuing operations		(145.1)	(4,820.5)	(318.6)
Net cash used in investing activities - discontinued operations		(0.8)	(1.9)	(2.0)
Net cash used in investing activities		(145.9)	(4,822.4)	(320.6)
Cash flows from financing activities:
Proceeds from long-term debt, net of discounts			2,491.6
Net proceeds from stock issuance	1,569.1		1,569.1
Repayment of long-term debt		(1,340.1)	(420.1)	(260.0)
Deferred financing fees		(3.9)	(79.5)
Treasury stock acquired		(1,276.2)		(494.4)
Tax benefit relating to employee stock-based compensation		58.9	13.4	42.1
Net proceeds from employee stock plans		35.3	12.5	31.9
Other		3.0
Net cash (used in) provided by financing activities		(2,523.0)	3,587.0	(680.4)
Effect of foreign currency translation adjustment		4.8	3.6	(6.0)
Net (decrease) increase in cash and cash equivalents		(546.7)	539.7	96.0
Cash and cash equivalents at beginning of year	530.7	1,070.4	530.7	434.7
Cash and cash equivalents at end of year		523.7	1,070.4	530.7
Express Scripts, Inc. [Member]
Condensed Consolidating Statement of Cash Flows
Net cash flows provided by (used in) operating activities		1,709.3	1,684.9	1,265.2
Cash flows from investing activities:
Acquisitions, net of cash acquired, and investment in joint venture			(8,881.7)	(251.5)
Purchase of short-term investments			(1,201.4)
Sale of short-term investments			1,198.9
Purchases of property and equipment		(53.1)	(116.6)	(66.8)
Proceeds from the sale of business				27.7
Other		17.6	6.4	(11.0)
Net cash used in investing activities - continuing operations		(35.5)	(8,994.4)	(301.6)
Net cash used in investing activities		(35.5)	(8,994.4)	(301.6)
Cash flows from financing activities:
Proceeds from long-term debt, net of discounts			2,491.6
Net proceeds from stock issuance			1,569.1
Repayment of long-term debt		(1,340.1)	(420.1)	(260.0)
Deferred financing fees		(3.9)	(79.5)
Treasury stock acquired		(1,276.2)		(494.4)
Tax benefit relating to employee stock-based compensation		58.9	13.4	42.1
Net proceeds from employee stock plans		35.3	12.5	31.9
Net transactions with parent		300.9	4,239.4	(181.4)
Other		3.0
Net cash (used in) provided by financing activities		(2,222.1)	7,826.4	(861.8)
Net (decrease) increase in cash and cash equivalents		(548.3)	516.9	101.8
Cash and cash equivalents at beginning of year	488.1	1,005.0	488.1	386.3
Cash and cash equivalents at end of year		456.7	1,005.0	488.1
Guarantors [Member]
Condensed Consolidating Statement of Cash Flows
Net cash flows provided by (used in) operating activities		773.2	385.2	84.6
Cash flows from investing activities:
Acquisitions, net of cash acquired, and investment in joint venture			(465.9)
Purchases of property and equipment		(61.3)	(22.6)	(9.7)
Other		(4.3)	(2.7)
Net cash used in investing activities - continuing operations		(65.6)	(491.2)	(9.7)
Net cash used in investing activities		(65.6)	(491.2)	(9.7)
Cash flows from financing activities:
Net transactions with parent		(708.6)	107.1	(82.4)
Net cash (used in) provided by financing activities		(708.6)	107.1	(82.4)
Net (decrease) increase in cash and cash equivalents		(1.0)	1.1	(7.5)
Cash and cash equivalents at beginning of year	8.9	10.0	8.9	16.4
Cash and cash equivalents at end of year		9.0	10.0	8.9
Non-Guarantors [Member]
Condensed Consolidating Statement of Cash Flows
Net cash flows provided by (used in) operating activities		16.8	13.6	48.0
Cash flows from investing activities:
Purchase of short-term investments		(38.0)
Purchases of property and equipment		(5.5)	(8.3)	(7.3)
Other		(0.5)	(1.6)
Net cash used in investing activities - continuing operations		(44.0)	(9.9)	(7.3)
Net cash used in investing activities - discontinued operations		(0.8)	(1.9)	(2.0)
Net cash used in investing activities		(44.8)	(11.8)	(9.3)
Cash flows from financing activities:
Net transactions with parent		25.8	16.3	(31.0)
Net cash (used in) provided by financing activities		25.8	16.3	(31.0)
Effect of foreign currency translation adjustment		4.8	3.6	(6.0)
Net (decrease) increase in cash and cash equivalents		2.6	21.7	1.7
Cash and cash equivalents at beginning of year	33.7	55.4	33.7	32.0
Cash and cash equivalents at end of year		58.0	55.4	33.7
Eliminations [Member]
Condensed Consolidating Statement of Cash Flows
Net cash flows provided by (used in) operating activities		(381.9)	(312.2)	(294.8)
Cash flows from investing activities:
Acquisitions, net of cash acquired, and investment in joint venture			4,675.0
Net cash used in investing activities - continuing operations			4,675.0
Net cash used in investing activities			4,675.0
Cash flows from financing activities:
Net transactions with parent		381.9	(4,362.8)	294.8
Net cash (used in) provided by financing activities		381.9	(4,362.8)	294.8
Cash and cash equivalents at beginning of year		0
Cash and cash equivalents at end of year		$ 0	$ 0

Net transactions with parent.

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Other cash flows provided by used in investing activities.

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Sale of short term investments.

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Includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits should not be reported as cash and cash equivalents.

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The net change between the beginning and ending balance of cash and cash equivalents.

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This element represents cash provided by (used in) the investing activities of the entity's discontinued operations during the period. This element should only be used by those entities that separately report cash flows attributable to discontinued operations. If using this element, it is an indication that the cash flows of the entity which are detailed in reconciling to cash provided by or used in investing activities reflect only cash flows attributable to continuing operations.

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The effect of exchange rate changes on cash balances held in foreign currencies.

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Reductions in the entity's income taxes that arise when compensation cost (from non-qualified share-based compensation) recognized on the entity's tax return exceeds compensation cost from share-based compensation recognized in financial statements. This element represents the cash inflow reported in the enterprise's financing activities.

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The net cash inflow (outflow) from financing activity for the period.

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The net cash inflow (outflow) from investing activity.

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The net cash from (used in) the entity's investing activities specifically EXCLUDING the cash flows derived by the entity from its discontinued operations, if any. This element is only to be used when the entity reports its cash flows attributable to discontinued operations separately from the cash flow provided by or used in investing activities. Such reporting would necessitate the entity to use the Net Cash Provided by (Used in) Discontinued Operations, Total element provided in the taxonomy.

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The net cash from (used in) all of the entity's operating activities, including those of discontinued operations, of the reporting entity. Operating activities generally involve producing and delivering goods and providing services. Operating activity cash flows include transactions, adjustments, and changes in value that are not defined as investing or financing activities.

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The cash outflow to reacquire common stock during the period.

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The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.

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The cash outflow associated with the acquisition of a controlling interest in another entity or an entity that is related to it but not strictly controlled (for example, an unconsolidated subsidiary, affiliate, joint venture or equity method investment).

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The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

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The cash outflow for securities or other assets acquired with excess cash, having ready marketability, which qualify for treatment as an investing activity based on management's intention and intended by management to be liquidated, if necessary, within the current operating cycle. Includes cash flows from securities classified as trading securities that were acquired for reasons other than sale in the short-term.

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This element represents the cash inflow during the period from the sale of a component of the entity.

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The cash inflow from the additional capital contribution to the entity.

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The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

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The net cash inflow (outflow) from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.

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The cash inflow associated with the amount received from the stock plan during the period.

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The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

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