SCHEDULE IV REINSURANCE Schedule IV - Reinsurance (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount, Life Insurance in Force	$ 152,502				$ 151,093				$ 152,502	$ 151,093	$ 146,610
Ceded to Other Companies, Life Insurance in Force	4,121				3,741				4,121	3,741	3,547
Assumed from Other Companies, Life Insurance in Force	0				0				0	0	0
Net Amount, Life Insurance in Force	$ 148,381				$ 147,352				$ 148,381	$ 147,352	$ 143,063
Percentage of Amount Assumed to Net, Life Insurance in Force	0.00%				0.00%				0.00%	0.00%	0.00%
Gross amount									$ 18,875	$ 19,592	$ 17,904
Ceded to Other Companies									566	608	520
Assumed from Other companies									222	241	186
Net Amount	$ 4,580	$ 4,648	$ 4,665	$ 4,638	$ 4,778	$ 5,022	$ 4,823	$ 4,602	$ 18,531	$ 19,225	$ 17,570
Percentage of Amount Assumed to Net									1.00%	1.00%	1.00%
Health insurance
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross amount									$ 14,829	$ 14,839	$ 13,604
Ceded to Other Companies									554	595	509
Assumed from Other companies									222	241	186
Net Amount									$ 14,497	$ 14,485	$ 13,281
Percentage of Amount Assumed to Net									1.00%	1.00%	1.00%
Life insurance
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross amount									$ 4,046	$ 4,753	$ 4,300
Ceded to Other Companies									12	13	11
Assumed from Other companies									0	0	0
Net Amount									$ 4,034	$ 4,740	$ 4,289
Percentage of Amount Assumed to Net									0.00%	0.00%	0.00%