Goodwill And Other Intangibles (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Goodwill acquired	$ 556	$ 783
Goodwill expected to be tax deductible	71
Goodwill	8,369	7,889	$ 7,241
Finite lived assets amortization expense	130	$ 109	$ 86
Risk and Insurance Services Segment
Segment Reporting Information [Line Items]
Goodwill acquired	321
Goodwill	5,900
Consulting Segment
Segment Reporting Information [Line Items]
Goodwill acquired	235
Goodwill	$ 2,500