Long-Term Commitments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Net rental costs	$ 393us-gaap_OperatingLeasesRentExpenseNet	$ 403us-gaap_OperatingLeasesRentExpenseNet	$ 416us-gaap_OperatingLeasesRentExpenseNet
Rentals from subleases	$ 12	$ 13	$ 10
Office Building [Member] \| Lease Concentration Risk [Member] \| Lease Obligations [Member]
Concentration Risk [Line Items]
Lease obligations for office space	98.00%

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

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-Publisher FASB

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- Definition

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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- Definition

The total amount of sublease rental income recognized during the period that reduces the entity's rent expense incurred under operating leases.

+ References

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