Restructuring Costs (Restructuring Activities) (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Restructuring Reserve [Roll Forward]
Liability at beginning of period	$ 92	$ 124
Amounts Accrued	5	12
Cash Paid	(12)	(43)
Other		(1)
Liability at end of period	85	92
Severance [Member]
Restructuring Reserve [Roll Forward]
Liability at beginning of period	7	11
Amounts Accrued	2	4
Cash Paid	(4)	(8)
Other		0
Liability at end of period	5	7
Future Rent Under Non-Cancelable Leases and Other Costs [Member]
Restructuring Reserve [Roll Forward]
Liability at beginning of period	85	113
Amounts Accrued	3	8
Cash Paid	(8)	(35)
Other		(1)
Liability at end of period	80	$ 85
Corporate Segment [Member]
Restructuring Reserve [Roll Forward]
Amounts Accrued	3
Risk and Insurance Services Segment [Member]
Restructuring Reserve [Roll Forward]
Amounts Accrued	$ 2