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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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Goodwill and Other Intangibles (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Goodwill acquired	$ 142	$ 97
Goodwill	14,412	9,739	$ 14,671	$ 9,599
Aggregate amortization expense	86	$ 51
Risk and Insurance Services Segment
Segment Reporting Information [Line Items]
Goodwill	11,300
Consulting Segment
Segment Reporting Information [Line Items]
Goodwill	$ 3,100