Available-for-sale securities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule of Available-for-sale Securities.
Cost Basis	$ 1,375	$ 1,293	$ 1,301
Unrealized pretax net gains (losses)	72	77	21
Fair Value	1,447	1,370	1,322
U.S. governmental agency
Schedule of Available-for-sale Securities.
Fair Value	310
U.S. treasury bonds
Schedule of Available-for-sale Securities.
Cost Basis	10	12	14
Fair Value	10	12	14
Other U.S. and non-U.S. government bonds
Schedule of Available-for-sale Securities.
Cost Basis	90	76	65
Unrealized pretax net gains (losses)	2	1
Fair Value	92	77	65
Corporate bonds
Schedule of Available-for-sale Securities.
Cost Basis	542	481	455
Unrealized pretax net gains (losses)	30	30	20
Fair Value	572	511	475
Asset-backed securities
Schedule of Available-for-sale Securities.
Cost Basis	112	136	141
Unrealized pretax net gains (losses)	(1)		(7)
Fair Value	111	136	134
U.S. governmental agency mortgage-backed securities
Schedule of Available-for-sale Securities.
Cost Basis	297	258	295
Unrealized pretax net gains (losses)	13	15	13
Fair Value	310	273	308
Residential mortgage-backed securities
Schedule of Available-for-sale Securities.
Cost Basis	33	43	61
Unrealized pretax net gains (losses)	(3)	(3)	(10)
Fair Value	30	40	51
Commercial mortgage-backed securities
Schedule of Available-for-sale Securities.
Cost Basis	142	164	175
Unrealized pretax net gains (losses)	3	4	(13)
Fair Value	145	168	162
Large capitalization value
Schedule of Available-for-sale Securities.
Cost Basis	127	100	76
Unrealized pretax net gains (losses)	21	22	13
Fair Value	148	122	89
Smaller company growth
Schedule of Available-for-sale Securities.
Cost Basis	22	23	19
Unrealized pretax net gains (losses)	7	8	5
Fair Value	$ 29	$ 31	$ 24

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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