The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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The amount of goodwill arising from a business combination that is expected to be deductible for tax purposes.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Goodwill And Other Intangibles (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2012
Segment Reporting Information [Line Items]
Goodwill acquired	$ 472us-gaap_GoodwillAcquiredDuringPeriod	$ 113us-gaap_GoodwillAcquiredDuringPeriod
Goodwill expected to be tax deductible	348
Goodwill	7,241us-gaap_Goodwill	6,893us-gaap_Goodwill	6,792us-gaap_Goodwill
Intangible asset impairment charge	0	5	8
Finite lived assets amortization expense	86us-gaap_AmortizationOfIntangibleAssets	72us-gaap_AmortizationOfIntangibleAssets	72us-gaap_AmortizationOfIntangibleAssets
Risk and Insurance Services Segment [Member]
Segment Reporting Information [Line Items]
Goodwill acquired	445
Goodwill	5,000
Intangible asset impairment charge				5
Consulting Segment [Member]
Segment Reporting Information [Line Items]
Goodwill acquired	27
Goodwill	$ 2,200