Investments (Troubled Debt Restructurings) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2011
Pre Modification:
Commercial And Other Loans Modifications Pre Modification Recorded Investment	$ 126
Commercial Mortgage and Other Loans Modifications Pre Modification Recorded Investment	383	383
Payment Default:
Commercial And Other Loans Modifications That Had Payment Default		1
Post Modification:
Commercial And Other Loans Modifications Post Modification Recorded Investment	112
Commercial Mortgage and Other Loans Modifications Post Modification Recorded Investment	338	338
Commercial Mortgage Loan [Member]
Pre Modification:
Commercial And Other Loans Modifications Pre Modification Recorded Investment	122
Commercial Mortgage and Other Loans Modifications Pre Modification Recorded Investment	366	366
Post Modification:
Commercial And Other Loans Modifications Post Modification Recorded Investment	108
Commercial Mortgage and Other Loans Modifications Post Modification Recorded Investment	321	321
Commercial Loan On Industrial [Member]
Pre Modification:
Commercial And Other Loans Modifications Pre Modification Recorded Investment	0
Commercial Mortgage and Other Loans Modifications Pre Modification Recorded Investment	0	0
Post Modification:
Commercial And Other Loans Modifications Post Modification Recorded Investment	0
Commercial Mortgage and Other Loans Modifications Post Modification Recorded Investment	0	0
Commercial Loan Retail [Member]
Pre Modification:
Commercial And Other Loans Modifications Pre Modification Recorded Investment	15
Commercial Mortgage and Other Loans Modifications Pre Modification Recorded Investment	151	151
Post Modification:
Commercial And Other Loans Modifications Post Modification Recorded Investment	15
Commercial Mortgage and Other Loans Modifications Post Modification Recorded Investment	134	134
Commercial Loan Office [Member]
Pre Modification:
Commercial And Other Loans Modifications Pre Modification Recorded Investment	17
Commercial Mortgage and Other Loans Modifications Pre Modification Recorded Investment	22	22
Post Modification:
Commercial And Other Loans Modifications Post Modification Recorded Investment	17
Commercial Mortgage and Other Loans Modifications Post Modification Recorded Investment	21	21
Commercial Loan Apartment And Multi Family [Member]
Pre Modification:
Commercial And Other Loans Modifications Pre Modification Recorded Investment	0
Commercial Mortgage and Other Loans Modifications Pre Modification Recorded Investment	38	38
Post Modification:
Commercial And Other Loans Modifications Post Modification Recorded Investment	0
Commercial Mortgage and Other Loans Modifications Post Modification Recorded Investment	36	36
Commercial Loan Hospitality [Member]
Pre Modification:
Commercial And Other Loans Modifications Pre Modification Recorded Investment	55
Commercial Mortgage and Other Loans Modifications Pre Modification Recorded Investment	86	86
Post Modification:
Commercial And Other Loans Modifications Post Modification Recorded Investment	46
Commercial Mortgage and Other Loans Modifications Post Modification Recorded Investment	75	75
Commercial Loan Other [Member]
Pre Modification:
Commercial And Other Loans Modifications Pre Modification Recorded Investment	35
Commercial Mortgage and Other Loans Modifications Pre Modification Recorded Investment	69	69
Post Modification:
Commercial And Other Loans Modifications Post Modification Recorded Investment	30
Commercial Mortgage and Other Loans Modifications Post Modification Recorded Investment	55	55
Agricultural Loans [Member]
Pre Modification:
Commercial And Other Loans Modifications Pre Modification Recorded Investment	2
Commercial Mortgage and Other Loans Modifications Pre Modification Recorded Investment	2	2
Post Modification:
Commercial And Other Loans Modifications Post Modification Recorded Investment	2
Commercial Mortgage and Other Loans Modifications Post Modification Recorded Investment	2	2
Residential Loans [Member]
Pre Modification:
Commercial And Other Loans Modifications Pre Modification Recorded Investment	2
Commercial Mortgage and Other Loans Modifications Pre Modification Recorded Investment	7	7
Post Modification:
Commercial And Other Loans Modifications Post Modification Recorded Investment	2
Commercial Mortgage and Other Loans Modifications Post Modification Recorded Investment	7	7
Other Collateralized Loan [Member]
Pre Modification:
Commercial And Other Loans Modifications Pre Modification Recorded Investment	0
Commercial Mortgage and Other Loans Modifications Pre Modification Recorded Investment	8	8
Post Modification:
Commercial And Other Loans Modifications Post Modification Recorded Investment	0
Commercial Mortgage and Other Loans Modifications Post Modification Recorded Investment	8	8
Uncollateralized Loan [Member]
Pre Modification:
Commercial And Other Loans Modifications Pre Modification Recorded Investment	0
Commercial Mortgage and Other Loans Modifications Pre Modification Recorded Investment	0	0
Post Modification:
Commercial And Other Loans Modifications Post Modification Recorded Investment	0
Commercial Mortgage and Other Loans Modifications Post Modification Recorded Investment	$ 0	$ 0