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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Goodwill and Other Intangibles (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Goodwill acquired	$ 17.0	$ 0.0
Goodwill	16,254.0	15,458.0	$ 16,317.0	$ 15,517.0
Aggregate amortization expense	91.0	$ 100.0
Risk and Insurance Services Segment
Segment Reporting Information [Line Items]
Goodwill acquired	17.0
Goodwill, expected tax deductible amount	1.6
Goodwill	12,500.0
Consulting Segment
Segment Reporting Information [Line Items]
Goodwill	$ 3,800.0