Schedule II - Aflac Incorporated (Parent Only) - Condensed Statements of Cash Flows (Detail) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
		Apr. 30, 2015	Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net earnings			$ 2,533		$ 2,951	$ 3,158
Adjustments to reconcile net earnings to net cash provided from operating activities:
Change in income tax liabilities			(36)		123	993
Other, net			989	[1]	309	401
Net cash provided (used) by operating activities			6,776		6,550	10,547
Cash flows from investing activities:
Fixed maturity securities sold			3,224		4,178	9,631
Fixed maturity securities purchased			(6,507)		(10,978)	(22,967)
Other investments sold (purchased)			(70)		272	(319)
Settlement of derivatives			(2,119)		(636)	(1,624)
Net cash provided (used) by investing activities			(4,897)		(4,241)	(11,091)
Cash flows from financing activities:
Purchases of treasury stock			(1,315)		(1,210)	(813)
Proceeds from borrowings			998		750	700
Principal payments under debt obligations			(1,272)		(335)	0
Dividends paid to shareholders			(656)		(654)	(635)
Treasury stock reissued			36		33	88
Other, net			(234)	[1]	16	6
Net cash provided (used) by financing activities			(2,187)		(147)	1,136
Net change in cash and cash equivalents			(308)		2,115	502
Cash and cash equivalents, beginning of period			4,658		2,543	2,041
Cash and cash equivalents, end of period			4,350		4,658	2,543
Parent Company
Cash flows from operating activities:
Net earnings			2,533		2,951	3,158
Adjustments to reconcile net earnings to net cash provided from operating activities:
Equity in undistributed earnings of subsidiaries	[2]		(291)		(1,281)	(1,986)
Change in income tax liabilities			6		115	155
Other, net			149	[3]	(72)	11
Net cash provided (used) by operating activities			2,397		1,713	1,338
Cash flows from investing activities:
Fixed maturity securities sold			121		38	8
Fixed maturity securities purchased			(202)		(105)	(206)
Other investments sold (purchased)			14		291	(298)
Settlement of derivatives			147		(1)	0
Additional capitalization of subsidiaries	[2]		(43)		0	0
Net cash provided (used) by investing activities			37		223	(496)
Cash flows from financing activities:
Purchases of treasury stock			(1,315)		(1,210)	(813)
Proceeds from borrowings			998		750	700
Principal payments under debt obligations			(1,272)		(335)	0
Dividends paid to shareholders			(656)		(654)	(635)
Treasury stock reissued			36		33	88
Proceeds from exercise of stock options			47		23	41
Net change in amount due from subsidiary	[2]		43		14	28
Other, net			(232)	[3]	0	0
Net cash provided (used) by financing activities			(2,351)		(1,379)	(591)
Net change in cash and cash equivalents			83		557	251
Cash and cash equivalents, beginning of period			1,638		1,081	830
Cash and cash equivalents, end of period			1,721		$ 1,638	$ 1,081
8.50% senior notes due May 2019
Condensed Cash Flow Statements, Captions [Line Items]
Expense on extinguishment of debt, make-whole premium		$ 230	$ 230
Cash flows from financing activities:
Principal payments under debt obligations		$ (850)

[1] Operating activities excludes and financing activities includes a cash outflow of $230 for the make-whole payment associated with the early extinguishment of debt

[2] Eliminated in consolidation

[3] Operating activities excludes and financing activities includes a cash outflow of $230 for the make-whole payment associated with the early extinguishment of debt