Fair Value (Assets and Liabilities measured at fair value on a recurring basis) (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Cash and cash equivalents	$ 9,429	$ 9,123
Total assets at fair value	27,975	25,745
Debt Securities [Member]
Available for sale securities	18,002	16,060
U.S. Government and Agency Obligations [Member]
Available for sale securities	2,373	2,234
State and Municipal Obligations [Member]
Available for sale securities	6,765	6,148
Corporate Obligations [Member]
Available for sale securities	6,007	5,310
U.S. Agency Mortgage-Backed Securities [Member]
Available for sale securities	2,353	1,903
Non-U.S. Agency Mortgage-Backed Securities [Member]
Available for sale securities	504	465
Equity Securities [Member]
Available for sale securities	544	516
Quoted Prices in Active Markets (Level 1) [Member]
Cash and cash equivalents	8,569	8,069
Total assets at fair value	10,469	9,921
Quoted Prices in Active Markets (Level 1) [Member] \| Debt Securities [Member]
Available for sale securities	1,567	1,546
Quoted Prices in Active Markets (Level 1) [Member] \| U.S. Government and Agency Obligations [Member]
Available for sale securities	1,551	1,515
Quoted Prices in Active Markets (Level 1) [Member] \| State and Municipal Obligations [Member]
Available for sale securities	0	0
Quoted Prices in Active Markets (Level 1) [Member] \| Corporate Obligations [Member]
Available for sale securities	16	31
Quoted Prices in Active Markets (Level 1) [Member] \| U.S. Agency Mortgage-Backed Securities [Member]
Available for sale securities	0	0
Quoted Prices in Active Markets (Level 1) [Member] \| Non-U.S. Agency Mortgage-Backed Securities [Member]
Available for sale securities	0	0
Quoted Prices in Active Markets (Level 1) [Member] \| Equity Securities [Member]
Available for sale securities	333	306
Other Observable Inputs (Level 2) [Member]
Cash and cash equivalents	860	1,054
Total assets at fair value	17,089	15,475
Other Observable Inputs (Level 2) [Member] \| Debt Securities [Member]
Available for sale securities	16,227	14,373
Other Observable Inputs (Level 2) [Member] \| U.S. Government and Agency Obligations [Member]
Available for sale securities	822	719
Other Observable Inputs (Level 2) [Member] \| State and Municipal Obligations [Member]
Available for sale securities	6,750	6,148
Other Observable Inputs (Level 2) [Member] \| Corporate Obligations [Member]
Available for sale securities	5,805	5,146
Other Observable Inputs (Level 2) [Member] \| U.S. Agency Mortgage-Backed Securities [Member]
Available for sale securities	2,353	1,903
Other Observable Inputs (Level 2) [Member] \| Non-U.S. Agency Mortgage-Backed Securities [Member]
Available for sale securities	497	457
Other Observable Inputs (Level 2) [Member] \| Equity Securities [Member]
Available for sale securities	2	2
Unobservable Inputs (Level 3) [Member]
Cash and cash equivalents	0	0
Total assets at fair value	417	349
Unobservable Inputs (Level 3) [Member] \| Debt Securities [Member]
Available for sale securities	208	141
Unobservable Inputs (Level 3) [Member] \| U.S. Government and Agency Obligations [Member]
Available for sale securities	0	0
Unobservable Inputs (Level 3) [Member] \| State and Municipal Obligations [Member]
Available for sale securities	15	0
Unobservable Inputs (Level 3) [Member] \| Corporate Obligations [Member]
Available for sale securities	186	133
Unobservable Inputs (Level 3) [Member] \| U.S. Agency Mortgage-Backed Securities [Member]
Available for sale securities	0	0
Unobservable Inputs (Level 3) [Member] \| Non-U.S. Agency Mortgage-Backed Securities [Member]
Available for sale securities	7	8
Unobservable Inputs (Level 3) [Member] \| Equity Securities [Member]
Available for sale securities	209	208
AARP Program [Member]
Cash and cash equivalents	267	115
Total assets at fair value	2,708	2,550
Other liabilities	76	59
Total liabilities at fair value	76	59
AARP Program [Member] \| Debt Securities [Member]
Available for sale securities	2,439	2,433
AARP Program [Member] \| U.S. Government and Agency Obligations [Member]
Available for sale securities	780	759
AARP Program [Member] \| State and Municipal Obligations [Member]
Available for sale securities	25	15
AARP Program [Member] \| Corporate Obligations [Member]
Available for sale securities	1,048	1,129
AARP Program [Member] \| U.S. Agency Mortgage-Backed Securities [Member]
Available for sale securities	436	393
AARP Program [Member] \| Non-U.S. Agency Mortgage-Backed Securities [Member]
Available for sale securities	150	137
AARP Program [Member] \| Equity Securities [Member]
Available for sale securities	2	2
AARP Program [Member] \| Quoted Prices in Active Markets (Level 1) [Member]
Cash and cash equivalents	257	115
Total assets at fair value	823	630
Other liabilities	27	0
Total liabilities at fair value	27	0
AARP Program [Member] \| Quoted Prices in Active Markets (Level 1) [Member] \| Debt Securities [Member]
Available for sale securities	566	515
AARP Program [Member] \| Quoted Prices in Active Markets (Level 1) [Member] \| U.S. Government and Agency Obligations [Member]
Available for sale securities	566	515
AARP Program [Member] \| Quoted Prices in Active Markets (Level 1) [Member] \| State and Municipal Obligations [Member]
Available for sale securities	0	0
AARP Program [Member] \| Quoted Prices in Active Markets (Level 1) [Member] \| Corporate Obligations [Member]
Available for sale securities	0	0
AARP Program [Member] \| Quoted Prices in Active Markets (Level 1) [Member] \| U.S. Agency Mortgage-Backed Securities [Member]
Available for sale securities	0	0
AARP Program [Member] \| Quoted Prices in Active Markets (Level 1) [Member] \| Non-U.S. Agency Mortgage-Backed Securities [Member]
Available for sale securities	0	0
AARP Program [Member] \| Quoted Prices in Active Markets (Level 1) [Member] \| Equity Securities [Member]
Available for sale securities	0	0
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member]
Cash and cash equivalents	10	0
Total assets at fair value	1,885	1,920
Other liabilities	49	0
Total liabilities at fair value	49	0
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| Debt Securities [Member]
Available for sale securities	1,873	1,918
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| U.S. Government and Agency Obligations [Member]
Available for sale securities	214	244
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| State and Municipal Obligations [Member]
Available for sale securities	25	15
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| Corporate Obligations [Member]
Available for sale securities	1,048	1,129
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| U.S. Agency Mortgage-Backed Securities [Member]
Available for sale securities	436	393
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| Non-U.S. Agency Mortgage-Backed Securities [Member]
Available for sale securities	150	137
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| Equity Securities [Member]
Available for sale securities	2	2
AARP Program [Member] \| Unobservable Inputs (Level 3) [Member]
Cash and cash equivalents	0	0
Total assets at fair value	0	0
Other liabilities	0	59
Total liabilities at fair value	0	59
AARP Program [Member] \| Unobservable Inputs (Level 3) [Member] \| Debt Securities [Member]
Available for sale securities	0	0
AARP Program [Member] \| Unobservable Inputs (Level 3) [Member] \| U.S. Government and Agency Obligations [Member]
Available for sale securities	0	0
AARP Program [Member] \| Unobservable Inputs (Level 3) [Member] \| State and Municipal Obligations [Member]
Available for sale securities	0	0
AARP Program [Member] \| Unobservable Inputs (Level 3) [Member] \| Corporate Obligations [Member]
Available for sale securities	0	0
AARP Program [Member] \| Unobservable Inputs (Level 3) [Member] \| U.S. Agency Mortgage-Backed Securities [Member]
Available for sale securities	0	0
AARP Program [Member] \| Unobservable Inputs (Level 3) [Member] \| Non-U.S. Agency Mortgage-Backed Securities [Member]
Available for sale securities	0	0
AARP Program [Member] \| Unobservable Inputs (Level 3) [Member] \| Equity Securities [Member]
Available for sale securities	$ 0	$ 0

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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- Definition

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 includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

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