Schedule II - Aflac Incorporated (Parent Only) - Condensed Statements of Comprehensive Income (Loss) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Condensed Financial Statements, Captions [Line Items]
Net earnings	$ 2,866	$ 1,937	$ 2,328
Foreign currency translation adjustments:
Unrealized foreign currency translation gains (losses) during period - parent only	(287)	(18)	90
Unrealized gains (losses) on investment securities:
Unrealized holding gains (losses) on investment securities during period - parent only	1,660	566	370
Unrealized gains (losses) on derivatives during period	(22)	(33)	51
Pension liability adjustment during period	(20)	(65)	(32)
Total other comprehensive income (loss) before income taxes	1,828	1,604	900
Income tax expense (benefit) related to items of other comprehensive income (loss)	1,078	392	(32)
Other comprehensive income (loss), net of income taxes	750	1,212	932
Total comprehensive income (loss)	3,616	3,149	3,260
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net earnings	2,866	1,937	2,328
Foreign currency translation adjustments:
Unrealized foreign currency translation gains (losses) during period - parent only	95	(54)	(127)
Equity in unrealized foreign currency translation gains (losses) of subsidiaries during period	(382)	36	217
Unrealized gains (losses) on investment securities:
Unrealized holding gains (losses) on investment securities during period - parent only	15	11	7
Equity in unrealized holding gains (losses) on investment securities held by subsidiaries during period	1,645	555	363
Equity in reclassification adjustment for realized (gains) losses of subsidiaries included in net earnings	497	1,154	421
Unrealized gains (losses) on derivatives during period	(22)	(33)	51
Pension liability adjustment during period	(20)	(65)	(32)
Total other comprehensive income (loss) before income taxes	1,828	1,604	900
Income tax expense (benefit) related to items of other comprehensive income (loss)	1,078	392	(32)
Other comprehensive income (loss), net of income taxes	750	1,212	932
Total comprehensive income (loss)	$ 3,616	$ 3,149	$ 3,260