BUSINESS SEGMENT INFORMATION - Operations by Segment - Revenues (Details) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2015 USD ($)		Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) segment		Sep. 30, 2014 USD ($)
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of Reportable Insurance Business Segments | segment					2
Net earned premiums		$ 4,380		$ 4,841	$ 13,176		$ 14,583
Net investment income		784		841	2,343		2,511
Other income (loss)		(10)		38	8		48
Total revenues		5,040		5,736	15,553		17,214
Other non-operating income (loss)		(27)	[1]	27	(39)	[1]	7
Realized investment gains (losses), non-operating	[2]	(136)		6	(36)		42
Gain (loss) on change in fair value of derivative, interest rate component, operating		22		10	62		30
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		2,980		3,534	9,036		10,672
Net investment income		606		676	1,824		2,019
Other income (loss)		8		9	23		25
Total revenues		3,594		4,219	10,883		12,716
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		1,345		1,306	4,016		3,910
Net investment income		173		162	507		484
Other income (loss)		2		0	6		2
Total revenues		1,520		1,468	4,529		4,396
Other business segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		67		11	159		29
Total Business Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		5,181		5,698	15,571		17,141
Corporate
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		73		43	242		194
Intercompany eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		(51)		$ (38)	(185)		$ (170)
September twenty fifteen profit repatriation
Segment Reporting, Revenue Reconciling Item [Line Items]
Foreign currency transaction gain (loss), realized		$ (14)			$ (14)

[1] 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).

[2] 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