Schedule II - Aflac Incorporated (Parent Only) - Condensed Statements of Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Net earnings	$ 2,659	$ 2,533	$ 2,951
Foreign currency translation adjustments:
Unrealized foreign currency translation gains (losses) during period - parent only	283	360	(1,455)
Unrealized gains (losses) on investment securities:
Unrealized holding gains (losses) on investment securities during period - parent only	2,852	(2,534)	5,947
Pension liability adjustment during period	(45)	(20)	(76)
Total other comprehensive income (loss) before income taxes	3,040	(2,255)	4,345
Income tax expense (benefit) related to items of other comprehensive income (loss)	1,035	(901)	1,803
Other comprehensive income (loss), net of income taxes	2,005	(1,354)	2,542
Total comprehensive income (loss)	4,664	1,179	5,493
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net earnings	2,659	2,533	2,951
Foreign currency translation adjustments:
Unrealized foreign currency translation gains (losses) during period - parent only	0	3	39
Equity in unrealized foreign currency translation gains (losses) of subsidiaries during period	283	357	(1,494)
Unrealized gains (losses) on investment securities:
Unrealized holding gains (losses) on investment securities during period - parent only	2	(8)	9
Equity in unrealized holding gains (losses) on investment securities held by subsidiaries during period	2,850	(2,526)	5,938
Equity in reclassification adjustment for realized (gains) losses of subsidiaries included in net earnings	(53)	(61)	(54)
Unrealized gains (losses) on derivatives during period	3	0	(17)
Pension liability adjustment during period	(45)	(20)	(76)
Total other comprehensive income (loss) before income taxes	3,040	(2,255)	4,345
Income tax expense (benefit) related to items of other comprehensive income (loss)	1,035	(901)	1,803
Other comprehensive income (loss), net of income taxes	2,005	(1,354)	2,542
Total comprehensive income (loss)	$ 4,664	$ 1,179	$ 5,493