Goodwill and Other Intangibles (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Goodwill acquired	$ 5,124	$ 626
Goodwill expected to be tax deductible	213
Goodwill	14,671	9,599	$ 9,089
Aggregate amortization expense	314	$ 183	$ 169
Risk and insurance services
Segment Reporting Information [Line Items]
Goodwill acquired	5,000
Goodwill	11,700
Consulting Segment
Segment Reporting Information [Line Items]
Goodwill acquired	167
Goodwill	$ 3,000

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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- Definition

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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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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