Schedule II - Aflac Incorporated (Parent Only) - Condensed Statements of Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Net earnings		$ 2,533	$ 2,951	$ 3,158
Foreign currency translation adjustments:
Unrealized foreign currency translation gains (losses) during period - parent only		360	(1,455)	(1,588)
Unrealized gains (losses) on investment securities:
Unrealized holding gains (losses) on investment securities during period - parent only		(2,534)	5,947	(2,362)
Pension liability adjustment during period		(20)	(76)	157
Total other comprehensive income (loss) before income taxes		(2,255)	4,345	(3,859)
Income tax expense (benefit) related to items of other comprehensive income (loss)		(901)	1,803	(581)
Other comprehensive income (loss), net of income taxes	[1]	(1,354)	2,542	(3,278)
Total comprehensive income (loss)		1,179	5,493	(120)
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net earnings		2,533	2,951	3,158
Foreign currency translation adjustments:
Unrealized foreign currency translation gains (losses) during period - parent only		3	39	48
Equity in unrealized foreign currency translation gains (losses) of subsidiaries during period		357	(1,494)	(1,636)
Unrealized gains (losses) on investment securities:
Unrealized holding gains (losses) on investment securities during period - parent only		(8)	9	(12)
Equity in unrealized holding gains (losses) on investment securities held by subsidiaries during period		(2,526)	5,938	(2,350)
Equity in reclassification adjustment for realized (gains) losses of subsidiaries included in net earnings		(61)	(54)	(56)
Unrealized gains (losses) on derivatives during period		0	(17)	(10)
Pension liability adjustment during period		(20)	(76)	157
Total other comprehensive income (loss) before income taxes		(2,255)	4,345	(3,859)
Income tax expense (benefit) related to items of other comprehensive income (loss)		(901)	1,803	(581)
Other comprehensive income (loss), net of income taxes		(1,354)	2,542	(3,278)
Total comprehensive income (loss)		$ 1,179	$ 5,493	$ (120)

[1] All amounts in the table above are net of tax.