1.0.0.3 false Consolidated Statements of Cash Flows (USD $) In Millions false 1 $ false false Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 false 2 $ false false Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 false 3 $ false false Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 5 Cash flows from operating activities: 3 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperationsAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false 3 false false 0 0 false false No definition available. false 6 Net income 4 us-gaap_ProfitLoss us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 true true 1280300000 1280.3 false false 2 true true 1102900000 1102.9 false false 3 true true 912000000 912.0 false false No definition available. No authoritative reference available. false 8 Adjustments to reconcile net income to net cash provided by operating activities: 5 us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false 3 false false 0 0 false false No definition available. false 9 Depreciation 6 us-gaap_Depreciation us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 179000000 179.0 false false 2 false true 157700000 157.7 false false 3 false true 168900000 168.9 false false No definition available. No authoritative reference available. false 10 Amortization of intangibles 6 us-gaap_AmortizationOfIntangibleAssets us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 305600000 305.6 false false 2 false true 285100000 285.1 false false 3 false true 228100000 228.1 false false No definition available. No authoritative reference available. false 11 Deferred income taxes 6 us-gaap_DeferredIncomeTaxExpenseBenefit us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -222100000 -222.1 false false 2 false true -99600000 -99.6 false false 3 false true -134100000 -134.1 false false No definition available. No authoritative reference available. false 12 Stock-based compensation on employee stock plans 6 us-gaap_ShareBasedCompensation us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 146000000 146.0 false false 2 false true 131700000 131.7 false false 3 false true 102500000 102.5 false false No definition available. No authoritative reference available. false 13 Tax benefit on employee stock plans 6 us-gaap_TaxBenefitFromStockOptionsExercised us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 106200000 106.2 false false 2 false true 67900000 67.9 false false 3 false true 102200000 102.2 false false No definition available. No authoritative reference available. false 14 Excess tax benefits from stock-based compensation arrangements 6 us-gaap_ExcessTaxBenefitFromShareBasedCompensationOperatingActivities us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -64300000 -64.3 false false 2 false true -41800000 -41.8 false false 3 false true -69900000 -69.9 false false No definition available. No authoritative reference available. false 15 Other 6 us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesOther us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 138300000 138.3 false false 2 false true 110700000 110.7 false false 3 false true 65000000 65.0 false false No definition available. No authoritative reference available. false 16 Net changes in assets and liabilities (net of acquisition effects, 2008 and 2007 only): 5 us-gaap_IncreaseDecreaseInOperatingCapitalAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false 3 false false 0 0 false false No definition available. false 17 Manufacturer accounts receivable, net 6 mhs_IncreaseDecreaseInManufacturerAccountsReceivableNet mhs false credit duration monetary The net change in the total amount due to the entity within one year of the balance sheet date (or one operating cycle, if... false false false false false false false false false 1 false true 93400000 93.4 false false 2 false true -341200000 -341.2 false false 3 false true 25900000 25.9 false false The net change in the total amount due to the entity within one year of the balance sheet date (or one operating cycle, if longer) representing the billed and estimated unbilled amounts due from brand-name pharmaceutical manufacturers for earned rebates and other prescription services, as well as notes and loans receivable, and any other types of non client receivables, net of allowances established for the purpose of reducing such receivables to an amount that approximates their net realizable value. No authoritative reference available. false 18 Client accounts receivable, net 6 mhs_IncreaseDecreaseInClientAccountsReceivableNet mhs false credit duration monetary The net change in the total amount due to the entity within one year of the balance sheet date (or one operating cycle, if... false false false false false false false false false 1 false true -515400000 -515.4 false false 2 false true -418500000 -418.5 false false 3 false true 65000000 65.0 false false The net change in the total amount due to the entity within one year of the balance sheet date (or one operating cycle, if longer) from outside sources, primarily trade client accounts receivable net of allowances established for the purpose of reducing such receivables to an amount that approximates their net realizable value. Client accounts receivable, net, includes billed and estimated unbilled receivables from clients, as well as a reduction for rebates and guarantees payable to clients when such are settled on a net basis in the form of an invoice credit. [Note: In cases where rebates and guarantees are settled with the client on a net basis, and the rebates and guarantees payable are greater than the corresponding client accounts balances, the net liability is reclassified to client rebates and guarantees payable. When these payables are settled in the form of a check or wire, they are recorded on a gross basis and the entire liability is reflected in client rebates and guarantees payable.] Client accounts receivable also includes receivables from the Center for Medicare & Medicaid Services for Medco's Medicare Part D Prescription Drug Program product offerings and premiums from members. No authoritative reference available. false 19 Inventories, net 6 us-gaap_IncreaseDecreaseInInventories us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 571400000 571.4 false false 2 false true 93000000 93.0 false false 3 false true -218100000 -218.1 false false No definition available. No authoritative reference available. false 20 Prepaid expenses and other current assets 6 us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 259600000 259.6 false false 2 false true -39700000 -39.7 false false 3 false true -4900000 -4.9 false false No definition available. No authoritative reference available. false 21 Income taxes receivable 6 us-gaap_IncreaseDecreaseInIncomeTaxesReceivable us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 15100000 15.1 false false 2 false true 2600000 2.6 false false 3 false true -3100000 -3.1 false false No definition available. No authoritative reference available. false 22 Other noncurrent assets 6 us-gaap_IncreaseDecreaseInOtherOperatingAssets us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 12800000 12.8 false false 2 false true 17200000 17.2 false false 3 false true 2100000 2.1 false false No definition available. No authoritative reference available. false 23 Claims and other accounts payable 6 us-gaap_IncreaseDecreaseInAccountsPayable us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 627200000 627.2 false false 2 false true 54300000 54.3 false false 3 false true -119200000 -119.2 false false No definition available. No authoritative reference available. false 24 Client rebates and guarantees payable 6 mhs_IncreaseDecreaseInClientRebatesAndGuaranteesPayable mhs false debit duration monetary The net change in carrying value as of the balance sheet date of liabilities incurred, due within one year, for certain... false false false false false false false false false 1 false true 448200000 448.2 false false 2 false true 566500000 566.5 false false 3 false true 206100000 206.1 false false The net change in carrying value as of the balance sheet date of liabilities incurred, due within one year, for certain rebates and guarantees payable. In cases where rebates and guarantees payable are settled on a net basis, and the rebates and guarantees payable are greater than the corresponding client accounts balances, the net liability is reclassified to client rebates and guarantees payable. When these payables are settled in the form of a check or wire, they are recorded on a gross basis and the entire liability is reflected in client rebates and guarantees payable. [Note: When these payables are settled on a net basis in the form of an invoice credit they are recorded as a reduction to Client accounts receivable, net.] No authoritative reference available. false 25 Accrued expenses and other current and noncurrent liabilities 6 mhs_IncreaseDecreaseInAccruedExpensesAndOtherCurrentAndNoncurrentLiabilities mhs false debit duration monetary The net change during the reporting period in the aggregate amount of expenses incurred but not yet paid, as well as other... false false false false false false false false false 1 false true 120100000 120.1 false false 2 false true -13700000 -13.7 false false 3 false true 38500000 38.5 false false The net change during the reporting period in the aggregate amount of expenses incurred but not yet paid, as well as other current and noncurrent liabilities not listed separately due to materiality. No authoritative reference available. true 26 Net cash provided by operating activities 6 us-gaap_NetCashProvidedByUsedInOperatingActivities us-gaap true na duration monetary No definition available. false false false false false false false false false 1 false true 3501400000 3501.4 false false 2 false true 1635100000 1635.1 false false 3 false true 1367000000 1367.0 false false No definition available. No authoritative reference available. true 27 Cash flows from investing activities: 2 us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false 3 false false 0 0 false false No definition available. false 28 Capital expenditures 3 us-gaap_PaymentsToAcquireProductiveAssets us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -238800000 -238.8 false false 2 false true -286900000 -286.9 false false 3 false true -177700000 -177.7 false false No definition available. No authoritative reference available. false 29 Purchase of securities and other assets 3 mhs_PurchaseOfSecuritiesAndOtherAssets mhs false credit duration monetary The cash outflow associated with the purchase of all investments (debt, security, other), as well as payments to acquire... false false false false false false false false false 1 false true -153400000 -153.4 false false 2 false true -124800000 -124.8 false false 3 false true -181700000 -181.7 false false The cash outflow associated with the purchase of all investments (debt, security, other), as well as payments to acquire intangible assets during the period. No authoritative reference available. false 30 Acquisitions of businesses, net of cash acquired 3 us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true -126500000 -126.5 false false 3 false true -1530600000 -1530.6 false false No definition available. No authoritative reference available. false 31 Proceeds from sale of securities and other investments 3 us-gaap_ProceedsFromSaleOfShortTermInvestments us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 87200000 87.2 false false 2 false true 122000000 122.0 false false 3 false true 176200000 176.2 false false No definition available. No authoritative reference available. true 32 Net cash used by investing activities 3 us-gaap_NetCashProvidedByUsedInInvestingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -305000000 -305.0 false false 2 false true -416200000 -416.2 false false 3 false true -1713800000 -1713.8 false false No definition available. No authoritative reference available. true 33 Cash flows from financing activities: 2 us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false 3 false false 0 0 false false No definition available. false 34 Proceeds from long-term debt 3 us-gaap_ProceedsFromIssuanceOfLongTermDebt us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true 3295700000 3295.7 false false 3 false true 2400000000 2400.0 false false No definition available. No authoritative reference available. false 35 Repayments on long-term debt 3 us-gaap_RepaymentsOfLongTermDebt us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true -2210000000 -2210.0 false false 3 false true -688400000 -688.4 false false No definition available. No authoritative reference available. false 36 Proceeds from short-term debt 3 us-gaap_ProceedsFromOtherShortTermDebt us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 15800000 15.8 false false 2 false true 0 0 false false 3 false true 275000000 275.0 false false No definition available. No authoritative reference available. false 37 Repayments under accounts receivable financing facility 3 us-gaap_RepaymentsOfOtherShortTermDebt us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -600000000 -600.0 false false 2 false true 0 0 false false 3 false true 0 0 false false No definition available. No authoritative reference available. false 38 Debt issuance costs 3 us-gaap_PaymentsOfFinancingCosts us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -400000 -0.4 false false 2 false true -11200000 -11.2 false false 3 false true -1800000 -1.8 false false No definition available. No authoritative reference available. false 39 Settlement of cash flow hedge 3 us-gaap_PaymentsForProceedsFromHedgeFinancingActivities us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true -45400000 -45.4 false false 3 false true 0 0 false false No definition available. No authoritative reference available. false 40 Purchases of treasury stock 3 us-gaap_PaymentsForRepurchaseOfCommonStock us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -1238500000 -1238.5 false false 2 false true -2186100000 -2186.1 false false 3 false true -1960600000 -1960.6 false false No definition available. No authoritative reference available. false 41 Excess tax benefits from stock-based compensation arrangements 3 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 64300000 64.3 false false 2 false true 41800000 41.8 false false 3 false true 69900000 69.9 false false No definition available. No authoritative reference available. false 42 Net proceeds from employee stock plans 3 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 152200000 152.2 false false 2 false true 60600000 60.6 false false 3 false true 208300000 208.3 false false No definition available. No authoritative reference available. true 43 Net cash (used by) provided by financing activities 3 us-gaap_NetCashProvidedByUsedInFinancingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -1606600000 -1606.6 false false 2 false true -1054600000 -1054.6 false false 3 false true 302400000 302.4 false false No definition available. No authoritative reference available. true 44 Net increase (decrease) in cash and cash equivalents 2 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease us-gaap true na duration monetary No definition available. false false false false false false false false false 1 false true 1589800000 1589.8 false false 2 false true 164300000 164.3 false false 3 false true -44400000 -44.4 false false No definition available. No authoritative reference available. false 45 Cash and cash equivalents at beginning of year 1 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant monetary No definition available. false false false false false false true false false 1 false true 938400000 938.4 false false 2 false true 774100000 774.1 false false 3 false true 818500000 818.5 false false No definition available. No authoritative reference available. false 46 Cash and cash equivalents at end of year 1 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant monetary No definition available. false false false false false false false true false 1 false true 2528200000 2528.2 false false 2 false true 938400000 938.4 false false 3 false true 774100000 774.1 false false No definition available. No authoritative reference available. false 47 Supplemental disclosures of cash flow information: 1 mhs_SupplementalDisclosuresOfCashFlowInformation mhs false na duration string Supplemental disclosures of cash flow information false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false 3 false false 0 0 false false Supplemental disclosures of cash flow information false 48 Cash paid during the year for interest 2 us-gaap_InterestPaidNet us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 168200000 168.2 false false 2 false true 207100000 207.1 false false 3 false true 123400000 123.4 false false No definition available. No authoritative reference available. true 49 Cash paid during the year for income taxes 2 us-gaap_IncomeTaxesPaidNet us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 true true 913900000 913.9 false false 2 true true 748900000 748.9 false false 3 true true 668500000 668.5 false false No definition available. No authoritative reference available. true false 3 44 false HundredThousands UnKnown UnKnown false true