BUSINESS SEGMENT AND FOREIGN INFORMATION - Operations by Segment - Pretax Earnings (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended								12 Months Ended
		Apr. 30, 2015	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
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings											$ 4,073		$ 4,253	$ 4,399
Realized investment gains (losses), non-operating	[1]										55		171	389
Other non-operating income (loss)											(266)	[2],[3]	67	28
Earnings before income taxes			$ 1,110	$ 864	$ 874	$ 1,013	$ 1,075	$ 1,074	$ 1,238	$ 1,104	3,862		4,491	4,816
Income taxes applicable to pretax operating earnings											1,403		1,456	1,512
Effect of foreign currency translation on operating earnings											(198)		(117)	(357)
Gain (loss) on change in fair value of derivative, interest rate component, operating											85		44	10
Aflac Japan
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings											3,175		3,458	3,628
Aflac U.S.
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings											1,101		1,073	1,038
Other business segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings											14		(2)	(1)
Total Business Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings											4,290		4,529	4,665
Interest expense, noninsurance operations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings											(146)		(198)	(198)
Corporate and eliminations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings											(71)		$ (78)	$ (68)
8.50% senior notes due May 2019
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Expense on extinguishment of debt, make-whole premium		$ 230									230
Twenty Fifteen Profit Repatriation
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Foreign currency transaction gain (loss), realized											$ (20)

[1] Excluding a gain of $85 in 2015, $44 in 2014 and $10 in 2013 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] $230 for the make-whole payment associated with the early extinguishment of debt

[3] Includes a loss of $20 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).