Schedule II - Aflac Incorporated (Parent Only) - Condensed Statements of Cash Flows (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Cash flows from operating activities:
Net earnings	$ 2,951		$ 3,158		$ 2,866
Adjustments to reconcile net earnings to net cash provided from operating activities:
Change in income tax liabilities	123		993		712
Other, net	309		401		(138)
Net cash provided (used) by operating activities	6,550		10,547		14,952
Cash flows from investing activities:
Fixed maturity securities sold	4,178		9,631		7,385
Fixed maturity securities purchased	(10,978)		(22,967)		(19,533)
Other investments sold (purchased)	272		(319)		(6)
Net cash provided (used) by investing activities	(4,241)		(11,091)		(16,952)
Cash flows from financing activities:
Purchases of treasury stock	(1,210)		(813)		(118)
Proceeds from borrowings	750		700		1,506
Principal payments under debt obligations	(335)		0		(341)
Dividends paid to shareholders	(654)		(635)		(603)
Treasury stock reissued	33		88		32
Net change in amount due to/from subsidiaries	16		6		12
Net cash provided (used) by financing activities	(147)		1,136		1,945
Net change in cash and cash equivalents	2,115		502		(208)
Cash and cash equivalents, beginning of period	2,543		2,041		2,249
Cash and cash equivalents, end of period	4,658		2,543		2,041
Parent Company
Cash flows from operating activities:
Net earnings	2,951		3,158		2,866
Adjustments to reconcile net earnings to net cash provided from operating activities:
Equity in undistributed earnings of subsidiaries	(1,281)	[1]	(1,986)	[1]	(2,749)	[1]
Change in income tax liabilities	115		155		111
Other, net	(72)		11		(242)
Net cash provided (used) by operating activities	1,713		1,338		(14)
Cash flows from investing activities:
Fixed maturity securities sold	38		8		13
Fixed maturity securities purchased	(105)		(206)		(26)
Other investments sold (purchased)	290		(298)		(3)
Net cash provided (used) by investing activities	223		(496)		(16)
Cash flows from financing activities:
Purchases of treasury stock	(1,210)		(813)		(118)
Proceeds from borrowings	750		700		1,506
Principal payments under debt obligations	(335)		0		(380)
Dividends paid to shareholders	(654)		(635)		(603)
Treasury stock reissued	33		88		70
Proceeds from exercise of stock options	23		41		21
Net change in amount due to/from subsidiaries	14	[1]	28	[1]	(21)	[1]
Net cash provided (used) by financing activities	(1,379)		(591)		475
Net change in cash and cash equivalents	557		251		445
Cash and cash equivalents, beginning of period	1,081		830		385
Cash and cash equivalents, end of period	$ 1,638		$ 1,081		$ 830

[1] Eliminated in consolidation