SCHEDULE III SUPPLEMENTARY INSURANCE INFORMATION - (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	$ 8,511				$ 8,273				$ 8,511	$ 8,273
Future Policy Benefits & Unpaid Policy Claims	73,489				69,276				73,489	69,276
Unearned premiums	7,857				8,626				7,857	8,626
Other policyholders' funds	6,285				6,031				6,285	6,031
Premiums Earned, Net	4,394	$ 4,380	$ 4,364	$ 4,432	4,489	$ 4,841	$ 4,888	$ 4,854	17,570	19,072	$ 20,135
Net investment income	792	$ 784	$ 777	$ 782	808	$ 841	$ 843	$ 827	3,135	3,319	3,293
Benefits and claims, net									11,746	12,937	13,813
Amortization of deferred policy acquisition costs									1,066	1,108	1,074
Other Operating Expenses									4,198	4,192	4,236
Premiums Written									17,083	18,550	21,104
Aflac Japan
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	5,370				5,211				5,370	5,211	5,819
Future Policy Benefits & Unpaid Policy Claims	64,437				60,036				64,437	60,036
Unearned premiums	7,739				8,509				7,739	8,509
Other policyholders' funds	6,285				6,030				6,285	6,030
Premiums Earned, Net									12,046	13,861	14,982
Net investment income									2,436	2,662	2,651
Benefits and claims, net									8,705	10,084	10,924
Amortization of deferred policy acquisition costs									578	649	641
Other Operating Expenses									2,055	2,364	2,495
Premiums Written									11,740	13,352	15,960
Aflac U.S.
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	3,141				3,062				3,141	3,062	2,979
Future Policy Benefits & Unpaid Policy Claims	9,696				9,239				9,696	9,239
Unearned premiums	118				117				118	117
Other policyholders' funds	0				0				0	0
Premiums Earned, Net									5,347	5,211	5,153
Net investment income									678	645	632
Benefits and claims, net									2,873	2,853	2,889
Amortization of deferred policy acquisition costs									488	459	433
Other Operating Expenses									1,570	1,474	1,431
Premiums Written									5,343	5,198	5,144
All other
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	0				0				0	0
Future Policy Benefits & Unpaid Policy Claims	43				1				43	1
Unearned premiums	0				0				0	0
Other policyholders' funds	0				$ 1				0	1
Premiums Earned, Net									177	0	0
Net investment income									21	12	10
Benefits and claims, net									168	0	0
Amortization of deferred policy acquisition costs									0	0	0
Other Operating Expenses									573	354	310
Premiums Written									0	$ 0	$ 0
Intercompany eliminations
Supplementary Insurance Information, by Segment [Line Items]
Deferred policy acquisition costs	0								0
Future Policy Benefits & Unpaid Policy Claims	(687)								(687)
Unearned premiums	0								0
Other policyholders' funds	$ 0								$ 0