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	Sep. 30, 2012	Dec. 31, 2011
Cash and cash equivalents	$ 8,916	$ 9,429
Total assets at fair value	28,706	27,975
Debt Securities [Member]
Available-for-sale Securities	19,130	18,002
U.S. Government and Agency Obligations [Member]
Available-for-sale Securities	2,745	2,373
State and Municipal Obligations [Member]
Available-for-sale Securities	6,735	6,765
Corporate Obligations [Member]
Available-for-sale Securities	6,711	6,007
U.S. Agency Mortgage-Backed Securities [Member]
Available-for-sale Securities	2,435	2,353
Non-U.S. Agency Mortgage-Backed Securities [Member]
Available-for-sale Securities	504	504
Equity Securities [Member]
Available-for-sale Securities	643	544
Quoted Prices in Active Markets (Level 1) [Member]
Cash and cash equivalents	8,002	8,569
Total assets at fair value	10,351	10,469
Quoted Prices in Active Markets (Level 1) [Member] \| Debt Securities [Member]
Available-for-sale Securities	1,926	1,567
Quoted Prices in Active Markets (Level 1) [Member] \| U.S. Government and Agency Obligations [Member]
Available-for-sale Securities	1,923	1,551
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	3	16
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	423	333
Other Observable Inputs (Level 2) [Member]
Cash and cash equivalents	914	860
Total assets at fair value	18,131	17,089
Other Observable Inputs (Level 2) [Member] \| Debt Securities [Member]
Available-for-sale Securities	17,198	16,227
Other Observable Inputs (Level 2) [Member] \| U.S. Government and Agency Obligations [Member]
Available-for-sale Securities	822	822
Other Observable Inputs (Level 2) [Member] \| State and Municipal Obligations [Member]
Available-for-sale Securities	6,735	6,750
Other Observable Inputs (Level 2) [Member] \| Corporate Obligations [Member]
Available-for-sale Securities	6,708	5,805
Other Observable Inputs (Level 2) [Member] \| U.S. Agency Mortgage-Backed Securities [Member]
Available-for-sale Securities	2,435	2,353
Other Observable Inputs (Level 2) [Member] \| Non-U.S. Agency Mortgage-Backed Securities [Member]
Available-for-sale Securities	498	497
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	224	417
Unobservable Inputs (Level 3) [Member] \| Debt Securities [Member]
Available-for-sale Securities	6	208
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	0	15
Unobservable Inputs (Level 3) [Member] \| Corporate Obligations [Member]
Available-for-sale Securities	0	186
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	6	7
Unobservable Inputs (Level 3) [Member] \| Equity Securities [Member]
Available-for-sale Securities	218	209
AARP Program [Member]
Cash and cash equivalents	161	267
Total assets at fair value	2,737	2,708
Other liabilities	94	76
Total liabilities at fair value	94	76
AARP Program [Member] \| Debt Securities [Member]
Available-for-sale Securities	2,573	2,439
AARP Program [Member] \| U.S. Government and Agency Obligations [Member]
Available-for-sale Securities	794	780
AARP Program [Member] \| State and Municipal Obligations [Member]
Available-for-sale Securities	49	25
AARP Program [Member] \| Corporate Obligations [Member]
Available-for-sale Securities	1,130	1,048
AARP Program [Member] \| U.S. Agency Mortgage-Backed Securities [Member]
Available-for-sale Securities	450	436
AARP Program [Member] \| Non-U.S. Agency Mortgage-Backed Securities [Member]
Available-for-sale Securities	150	150
AARP Program [Member] \| Equity Securities [Member]
Available-for-sale Securities	3	2
AARP Program [Member] \| Quoted Prices in Active Markets (Level 1) [Member]
Cash and cash equivalents	161	257
Total assets at fair value	706	823
Other liabilities	26	27
Total liabilities at fair value	26	27
AARP Program [Member] \| Quoted Prices in Active Markets (Level 1) [Member] \| Debt Securities [Member]
Available-for-sale Securities	545	566
AARP Program [Member] \| Quoted Prices in Active Markets (Level 1) [Member] \| U.S. Government and Agency Obligations [Member]
Available-for-sale Securities	545	566
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	0	10
Total assets at fair value	2,031	1,885
Other liabilities	68	49
Total liabilities at fair value	68	49
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| Debt Securities [Member]
Available-for-sale Securities	2,028	1,873
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| U.S. Government and Agency Obligations [Member]
Available-for-sale Securities	249	214
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| State and Municipal Obligations [Member]
Available-for-sale Securities	49	25
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| Corporate Obligations [Member]
Available-for-sale Securities	1,130	1,048
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| U.S. Agency Mortgage-Backed Securities [Member]
Available-for-sale Securities	450	436
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| Non-U.S. Agency Mortgage-Backed Securities [Member]
Available-for-sale Securities	150	150
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| Equity Securities [Member]
Available-for-sale Securities	3	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	0
Total liabilities at fair value	0	0
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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