Schedule IV - Reinsurance (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount [Abstract]
Gross amount	$ 26,188	$ 19,219	$ 18,179
Ceded to other companies	469	447	437
Assumed from other companies	468	194	532
Net amount	26,187	18,966	18,274
Percentage of amount assumed to net	1.80%	1.00%	2.90%
Life Insurance in Force [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount [Abstract]
Gross amount	710,140	606,587	566,841
Ceded to other companies	52,435	53,088	44,335
Assumed from other companies	8,168	9,163	9,734
Net amount	665,873	562,662	532,240
Percentage of amount assumed to net	1.20%	1.60%	1.80%
Life Insurance Segment [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount [Abstract]
Gross amount	2,025	1,990	2,026
Ceded to other companies	268	280	264
Assumed from other companies	29	40	107
Net amount	1,786	1,750	1,869
Percentage of amount assumed to net	1.60%	2.30%	5.70%
Accident and Health Insurance Segment [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount [Abstract]
Gross amount	24,163	17,229	16,153
Ceded to other companies	201	167	173
Assumed from other companies	439	154	425
Net amount	$ 24,401	$ 17,216	$ 16,405
Percentage of amount assumed to net	1.80%	0.90%	2.60%