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	Mar. 31, 2013	Dec. 31, 2012
Cash and cash equivalents	$ 10,038	$ 8,406
Total assets at fair value	30,249	28,323
Debt Securities [Member]
Available-for-sale Securities	19,464	19,226
U.S. Government and Agency Obligations [Member]
Available-for-sale Securities	2,471	2,538
State and Municipal Obligations [Member]
Available-for-sale Securities	6,687	6,667
Corporate Obligations [Member]
Available-for-sale Securities	7,573	7,209
U.S. Agency Mortgage-Backed Securities [Member]
Available-for-sale Securities	2,074	2,238
Non-U.S. Agency Mortgage-Backed Securities [Member]
Available-for-sale Securities	659	574
Equity Securities [Member]
Available-for-sale Securities	726	677
Quoted Prices in Active Markets (Level 1) [Member]
Cash and cash equivalents	9,301	7,615
Total assets at fair value	11,529	9,830
Quoted Prices in Active Markets (Level 1) [Member] \| Debt Securities [Member]
Available-for-sale Securities	1,755	1,765
Quoted Prices in Active Markets (Level 1) [Member] \| U.S. Government and Agency Obligations [Member]
Available-for-sale Securities	1,748	1,752
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	7	13
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	473	450
Other Observable Inputs (Level 2) [Member]
Cash and cash equivalents	737	791
Total assets at fair value	18,449	18,252
Other Observable Inputs (Level 2) [Member] \| Debt Securities [Member]
Available-for-sale Securities	17,677	17,444
Other Observable Inputs (Level 2) [Member] \| U.S. Government and Agency Obligations [Member]
Available-for-sale Securities	723	786
Other Observable Inputs (Level 2) [Member] \| State and Municipal Obligations [Member]
Available-for-sale Securities	6,687	6,667
Other Observable Inputs (Level 2) [Member] \| Corporate Obligations [Member]
Available-for-sale Securities	7,540	7,185
Other Observable Inputs (Level 2) [Member] \| U.S. Agency Mortgage-Backed Securities [Member]
Available-for-sale Securities	2,074	2,238
Other Observable Inputs (Level 2) [Member] \| Non-U.S. Agency Mortgage-Backed Securities [Member]
Available-for-sale Securities	653	568
Other Observable Inputs (Level 2) [Member] \| Equity Securities [Member]
Available-for-sale Securities	14	3
AARP Program [Member]
Cash and cash equivalents	57	230
Total assets at fair value	2,659	2,773
Other liabilities	71	81
AARP Program [Member] \| Debt Securities [Member]
Available-for-sale Securities	2,599	2,540
AARP Program [Member] \| U.S. Government and Agency Obligations [Member]
Available-for-sale Securities	749	789
AARP Program [Member] \| State and Municipal Obligations [Member]
Available-for-sale Securities	57	51
AARP Program [Member] \| Corporate Obligations [Member]
Available-for-sale Securities	1,200	1,118
AARP Program [Member] \| U.S. Agency Mortgage-Backed Securities [Member]
Available-for-sale Securities	446	427
AARP Program [Member] \| Non-U.S. Agency Mortgage-Backed Securities [Member]
Available-for-sale Securities	147	155
AARP Program [Member] \| Equity Securities [Member]
Available-for-sale Securities	3	3
AARP Program [Member] \| Quoted Prices in Active Markets (Level 1) [Member]
Cash and cash equivalents	57	230
Total assets at fair value	563	775
Other liabilities	20	23
AARP Program [Member] \| Quoted Prices in Active Markets (Level 1) [Member] \| Debt Securities [Member]
Available-for-sale Securities	506	545
AARP Program [Member] \| Quoted Prices in Active Markets (Level 1) [Member] \| U.S. Government and Agency Obligations [Member]
Available-for-sale Securities	506	545
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	0
Total assets at fair value	2,096	1,998
Other liabilities	51	58
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| Debt Securities [Member]
Available-for-sale Securities	2,093	1,995
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| U.S. Government and Agency Obligations [Member]
Available-for-sale Securities	243	244
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| State and Municipal Obligations [Member]
Available-for-sale Securities	57	51
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| Corporate Obligations [Member]
Available-for-sale Securities	1,200	1,118
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| U.S. Agency Mortgage-Backed Securities [Member]
Available-for-sale Securities	446	427
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| Non-U.S. Agency Mortgage-Backed Securities [Member]
Available-for-sale Securities	147	155
AARP Program [Member] \| Other Observable Inputs (Level 2) [Member] \| Equity Securities [Member]
Available-for-sale Securities	$ 3	$ 3

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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