Acquisitions and Sales of Businesses (Details 1) (Medicare supplement and critical illness businesses [Member], USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
	Aug. 31, 2012	Dec. 31, 2012
Medicare supplement and critical illness businesses [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale proceeds	$ 326	$ 326
Expenses	(11)
Net proceeds	315
Assets of businesses sold:
Cash and investments	217
Deferred policy acquisition costs	108
Other assets	31
Total assets	356
Liabilities of businesses sold:
Life, accident and health reserves	209
Other liabilities	2
Total liabilities	211
Net assets of businesses sold	145
Gain on sale of subsidiaries	$ 170	$ 170