Acquisitions and Dispositions - Acquisitions (Details) (USD $) In Millions, unless otherwise specified					3 Months Ended		6 Months Ended			6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014 Business Acquisition 1 [Member]	Jun. 30, 2013 Business Acquisition 1 [Member]	Jun. 30, 2014 Risk Solutions [Member] business	Jun. 30, 2013 Risk Solutions [Member] business	Jun. 30, 2014 Risk Solutions [Member] business	Jun. 30, 2013 Risk Solutions [Member] business	Dec. 31, 2013 Risk Solutions [Member]	Jun. 30, 2014 HR Solutions [Member] business	Jun. 30, 2013 HR Solutions [Member] business	Dec. 31, 2013 HR Solutions [Member]	Jul. 15, 2014 Subsequent Event [Member] state employee
Business Acquisition
Entity Number of Employees													800
Number of business acquired under business combination					2	4	3	4		1	1
Consideration			$ 83	$ 23
Intangible assets:
Goodwill	9,099	8,997	52	16	6,107		6,107		6,020	2,992		2,977
Other intangible assets			48	11
Total			$ 100	$ 27
Policies Issued, Number of States													50