Financial Instruments (Fair Value of Derivative Instruments Table) (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Financial Instruments
Fair value of derivative instruments under collateralized arrangements in a liability position	$ 21	$ 216
Collateral posted on derivative instruments	0	0
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	1,432	719
Fair value of total derivative liabilities and debt	7,963	6,802
Maximum spread on credit default swap agreements before full collateralization is required (in percent)	2.50%
Liabilities included in master netting arrangements	97	251
Net exposure related to derivative assets recorded in the Statement of Financial Position	817us-gaap_DerivativeAssets	439us-gaap_DerivativeAssets
Net exposure related to derivative liabilities recorded in the Statement of Financial Position	99us-gaap_DerivativeLiabilities	250us-gaap_DerivativeLiabilities
Cash collateral rehypothecated	0ibm_CashCollateralRehypothecated	0ibm_CashCollateralRehypothecated
U.S. Treasury securities
Fair Values of Derivative Instruments
Non-cash collateral received	31	0
Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	1,281	522
Fair value of total derivative instruments, Liabilities	72	456
Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	151	197
Fair value of total derivative instruments, Liabilities	125	45
Other receivables
Fair Values of Derivative Instruments
Cash collateral issued, derivatives	0	0
Accounts payable
Fair Values of Derivative Instruments
Obligation to return cash collateral	487	29
Prepaid expenses and other current assets \| Interest rate contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	5
Prepaid expenses and other current assets \| Foreign exchange contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	632	187
Prepaid expenses and other current assets \| Foreign exchange contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	90	94
Prepaid expenses and other current assets \| Equity contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	24	36
Investments and sundry assets \| Interest rate contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	628	308
Investments and sundry assets \| Foreign exchange contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	17	26
Investments and sundry assets \| Foreign exchange contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	37	67
Investments and sundry assets \| Equity contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Assets	0
Other accrued expenses and liabilities \| Interest rate contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	0	0
Other accrued expenses and liabilities \| Foreign exchange contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	50	331
Other accrued expenses and liabilities \| Foreign exchange contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	101	40
Other accrued expenses and liabilities \| Equity contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	14	4
Other liabilities \| Interest rate contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities		13
Other liabilities \| Foreign exchange contracts \| Designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	21	112
Other liabilities \| Foreign exchange contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	4	1
Other liabilities \| Equity contracts \| Derivative instruments not designated as hedging instruments
Fair Values of Derivative Instruments
Fair value of total derivative instruments, Liabilities	5
Long term debt \| Designated as hedging instruments \| Net investment hedge
Fair Values of Derivative Instruments
Debt designated as hedging instrument	7,766	6,111
Short term debt \| Designated as hedging instruments \| Net investment hedge
Fair Values of Derivative Instruments
Debt designated as hedging instrument	$ 0	$ 190

This item represents the amount of cash collateral rehypothecated as of the balance sheet date.

No definition available.

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- Definition

The credit default swap spread which, if exceeded, would trigger contingent features of these agreements.

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- Definition

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and elected not to be offset.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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- Definition

Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets.

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Amount of obligation to return securities collateral under master netting arrangements that have not been offset against derivative assets.

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Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and elected not to be offset.

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Fair value of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be offset, deducted from derivative liabilities.

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The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

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Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

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