Commitments: (Details 2) (USD $) In Millions, unless otherwise specified			3 Months Ended
Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Extended warranty	Mar. 31, 2012 Extended warranty
Movement in extended warranty liability
Beginning balance, aggregate deferred revenue			$ 606	$ 636
Revenue deferred for new extended warranty contracts			47	54
Amortization of deferred revenue			(82)	(76)
Other			(7)	3
Ending balance, aggregate deferred revenue			565	616
Deferred revenue:
Deferred income, current portion	12,971	11,952	286	292
Deferred income, noncurrent portion	4,409	4,491	278	323
Aggregate deferred revenue			$ 565	$ 616

Amount of other changes to deferred revenue during the period, including foreign currency translation adjustments.

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Amount of deferred revenue as of balance sheet date. Deferred revenue represents collections of cash or other assets related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

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Amount of deferred revenue recognized for transactions arising during the current reporting period. Deferred revenue is a liability as of the balance sheet date related to a revenue producing activity for which revenue has not yet been recognized. Generally, an Entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

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The carrying amount of consideration received or receivable as of the balance sheet date on potential earnings that were not recognized as revenue in conformity with GAAP, and which are expected to be recognized as such within one year or the normal operating cycle, if longer, including sales, license fees, and royalties, but excluding interest income.

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The noncurrent portion of deferred revenue amount as of balance sheet date. Deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized, and is not expected to be recognized in the next twelve months. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

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Amount of previously reported deferred or unearned revenue that was recognized as revenue during the period. Deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

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