Schedule II - Aflac Incorporated (Parent Only) - Condensed Statements of Cash Flows (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Cash flows from operating activities:
Net earnings		$ 2,659		$ 2,533		$ 2,951
Adjustments to reconcile net earnings to net cash provided from operating activities:
Change in income tax liabilities		(93)		(36)		123
Other, net		231	[1]	989	[1]	309
Net cash provided (used) by operating activities		5,987		6,776		6,550
Cash flows from investing activities:
Fixed maturity securities sold		5,157		3,224		4,178
Fixed maturity securities purchased		(10,890)		(6,507)		(10,978)
Other investments sold (purchased)		(1,118)		(70)		272
Settlement of derivatives		1,252		(2,119)		(636)
Payments for (Proceeds from) Other Investing Activities		(76)		(86)		30
Net cash provided (used) by investing activities		(3,855)		(4,897)		(4,241)
Cash flows from financing activities:
Purchases of treasury stock		(1,422)		(1,315)		(1,210)
Proceeds from borrowings		986		998		750
Principal payments under debt obligations		(610)		(1,272)		(335)
Dividends paid to shareholders		(658)		(656)		(654)
Treasury stock reissued		46		36		33
Other, net		(120)	[1]	(234)	[1]	16
Net cash provided (used) by financing activities		(1,619)		(2,187)		(147)
Net change in cash and cash equivalents		509		(308)		2,115
Cash and cash equivalents, beginning of period		4,350		4,658		2,543
Cash and cash equivalents, end of period		4,859		4,350		4,658
Parent Company
Cash flows from operating activities:
Net earnings		2,659		2,533		2,951
Adjustments to reconcile net earnings to net cash provided from operating activities:
Equity in undistributed earnings of subsidiaries	[2]	(814)		(291)		(1,281)
Change in income tax liabilities		(112)		6		115
Other, net		406	[3]	149	[3]	(72)
Net cash provided (used) by operating activities		2,139		2,397		1,713
Cash flows from investing activities:
Fixed maturity securities sold		225		121		38
Fixed maturity securities purchased		(229)		(202)		(105)
Other investments sold (purchased)		6		14		291
Settlement of derivatives		0		147		(1)
Additional capitalization of subsidiaries	[2]	(36)		(43)		0
Payments for (Proceeds from) Other Investing Activities		(25)		0		0
Net cash provided (used) by investing activities		(59)		37		223
Cash flows from financing activities:
Purchases of treasury stock		(1,422)		(1,315)		(1,210)
Proceeds from borrowings		986		998		750
Principal payments under debt obligations		(621)		(1,272)		(335)
Dividends paid to shareholders		(658)		(656)		(654)
Treasury stock reissued		46		36		33
Proceeds from exercise of stock options		36		47		23
Net change in amount due to/from subsidiary	[2]	(6)		43		14
Other, net		(125)	[3]	(232)	[3]	0
Net cash provided (used) by financing activities		(1,764)		(2,351)		(1,379)
Net change in cash and cash equivalents		316		83		557
Cash and cash equivalents, beginning of period		1,721		1,638		1,081
Cash and cash equivalents, end of period		2,037		1,721		$ 1,638
Senior Notes due 2039 and 2040
Condensed Cash Flow Statements, Captions [Line Items]
Expense on extinguishment of debt		$ 137
8.50% senior notes due May 2019
Condensed Cash Flow Statements, Captions [Line Items]
Expense on extinguishment of debt				$ 230

[1] Operating activities excludes and financing activities includes a cash outflow of $137 in 2016 and $230 in 2015 for the payments associated with the early extinguishment of debt

[2] Eliminated in consolidation

[3] Operating activities excludes and financing activities includes a cash outflow of $137 in 2016 and $230 in 2015 for the payments associated with the early extinguishment of debt