Quarterly Financial Data (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Consolidated Quarterly Results [Abstract]
Total revenues	$ 9,467us-gaap_Revenues	$ 8,496us-gaap_Revenues
Income before income taxes	854	853
Shareholders' net income	$ 533	$ 528
Shareholders' Net Income Per Share:
EPS, basic	$ 2.08us-gaap_EarningsPerShareBasic	$ 1.96us-gaap_EarningsPerShareBasic
EPS, diluted	$ 2.04us-gaap_EarningsPerShareDiluted	$ 1.92us-gaap_EarningsPerShareDiluted
Stock And Dividend Data [Abstract]
Dividends Declared Per Share	$ 0.04	$ 0.04

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Aggregate dividends declared during the period for each share of common stock outstanding.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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