Schedule II - Aflac Incorporated (Parent Only) - Condensed Statements of Comprehensive Income (Loss) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Net earnings	$ 2,951		$ 3,158		$ 2,866
Foreign currency translation adjustments:
Unrealized foreign currency translation gains (losses) during period - parent only	(1,455)		(1,588)		(287)
Unrealized gains (losses) on investment securities:
Unrealized holding gains (losses) on investment securities during period - parent only	5,947		(2,362)		1,660
Pension liability adjustment during period	(76)		157		(20)
Total other comprehensive income (loss) before income taxes	4,345		(3,859)		1,828
Income tax expense (benefit) related to items of other comprehensive income (loss)	1,803		(581)		1,078
Other comprehensive income (loss), net of income taxes	2,542	[1]	(3,278)	[1]	750
Total comprehensive income (loss)	5,493		(120)		3,616
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net earnings	2,951		3,158		2,866
Foreign currency translation adjustments:
Unrealized foreign currency translation gains (losses) during period - parent only	39		48		95
Equity in unrealized foreign currency translation gains (losses) of subsidiaries during period	(1,494)		(1,636)		(382)
Unrealized gains (losses) on investment securities:
Unrealized holding gains (losses) on investment securities during period - parent only	9		(12)		15
Equity in unrealized holding gains (losses) on investment securities held by subsidiaries during period	5,938		(2,350)		1,645
Equity in reclassification adjustment for realized (gains) losses of subsidiaries included in net earnings	(54)		(56)		497
Unrealized gains (losses) on derivatives during period	(17)		(10)		(22)
Pension liability adjustment during period	(76)		157		(20)
Total other comprehensive income (loss) before income taxes	4,345		(3,859)		1,828
Income tax expense (benefit) related to items of other comprehensive income (loss)	1,803		(581)		1,078
Other comprehensive income (loss), net of income taxes	2,542		(3,278)		750
Total comprehensive income (loss)	$ 5,493		$ (120)		$ 3,616

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