Goodwill And Other Intangibles (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Goodwill acquired	$ 783	$ 472
Goodwill expected to be tax deductible	387
Goodwill	7,889	7,241	$ 6,893
Finite lived assets amortization expense	109	$ 86	$ 72
Risk and Insurance Services Segment
Segment Reporting Information [Line Items]
Goodwill acquired	639
Goodwill	5,600
Consulting Segment
Segment Reporting Information [Line Items]
Goodwill acquired	144
Goodwill	$ 2,300