BUSINESS SEGMENT INFORMATION - Operations by Segment - Pretax Earnings (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended			9 Months Ended
		Apr. 30, 2015	Sep. 30, 2015		Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings			$ 1,027		$ 1,041	$ 3,058		$ 3,367
Realized investment gains (losses), non-operating	[1]		(136)		6	(36)		42
Other non-operating income (loss)			(27)	[2]	27	(270)	[2],[3]	7
Earnings before income taxes			864		1,074	2,752		3,416
Income taxes applicable to pretax operating earnings			355		356	1,057		1,151
Effect of foreign currency translation on operating earnings			(58)		(19)	(175)		(80)
Gain (loss) on change in fair value of derivative, interest rate component, operating			22		10	62		30
Gain (Loss) on Investments			(114)		16	26		72
Aflac Japan
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings			789		828	2,365		2,688
Aflac U.S.
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings			286		269	864		872
Other business segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings			5		0	10		0
Total Business Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings			1,080		1,097	3,239		3,560
Interest expense, noninsurance operations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings			(30)		(49)	(117)		(150)
Corporate and eliminations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings			(23)		$ (7)	(64)		$ (43)
8.50% senior notes due May 2019
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Extinguishment of debt, make-whole premium		$ 230				230
September twenty fifteen profit repatriation
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Foreign currency transaction gain (loss), realized			$ (14)			$ (14)

[1] Excluding a gain of $22 and $10 for the three-month periods and $62 and $30 for the nine-month periods ended September 30, 2015, and 2014, respectively, related to the interest rate component of the change in fair value of foreign currency swaps on notes payable which is classified as an operating gain when analyzing segment operations

[2] Includes a loss of $14 for the three- and nine-month periods ended September 30, 2015, related to the change in value of yen repatriation received in advance of settlement of certain foreign currency derivatives. This loss was offset by derivative gains included in realized investment gains (losses).

[3] Includes a cash outflow of $230 for the make-whole payment associated with the early extinguishment of debt