Consolidated statements of comprehensive income (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Available-for-sale investments:
Unrealized gains (losses), tax	$ 1	$ (3)	$ (9)
Reclassification of recognized transactions, tax	(7)	0	(3)
Net actuarial gains (losses) of defined benefit plans:
Adjustment, tax	65	61	(38)
Reclassification of recognized transactions, tax	(28)	(36)	(27)
Prior service cost of defined benefit plans:
Adjustment, tax	5	(1)	1
Reclassification of recognized transactions, tax	(1)	0	3
Change in fair value of derivative instrument, tax benefit (expense)	$ 1	$ 0	$ 0

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Tax effect on the accumulated change in the value of either the projected benefit obligation or plan assets resulting from experience different from that assumed or from a change in an actuarial assumption that has not been recognized in net periodic benefit cost.

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Tax effect on adjustment out of other comprehensive income for prior service costs recognized as a component of net period benefit cost during the period.

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For each annual statement of income presented, the tax effect of the net gain (loss) recognized in other comprehensive income that is a reclassification adjustment of other comprehensive income as a result of being recognized as a component of net periodic benefit cost for the period.

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Tax effect on the change in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses.

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