Schedule II - Aflac Incorporated (Parent Only) - Condensed Statement of Earnings (Detail) - USD ($) $ in Millions		1 Months Ended	3 Months Ended								12 Months Ended
		Apr. 30, 2015	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013
Condensed Income Statements, [Line Items]
Net investment income			$ 792	$ 784	$ 777	$ 782	$ 808	$ 841	$ 843	$ 827	$ 3,135		$ 3,319	$ 3,293
Realized investment gains (losses)											140		215	399
Total revenues			5,319	5,040	5,287	5,226	5,514	5,736	5,838	5,640	20,872		22,728	23,939
Interest expense											289		317	293
Other operating expenses											392	[1]	178	193
Earnings before income taxes			1,110	864	874	1,013	1,075	1,074	1,238	1,104	3,862		4,491	4,816
Current tax expense (benefit)											1,288		1,079	1,236
Deferred tax expense (benefit)											41		461	422
Total income tax expense			$ 380	$ 297	$ 301	$ 350	$ 372	$ 368	$ 428	$ 372	1,329		1,540	1,658
Net earnings											2,533		2,951	3,158
Parent Company
Condensed Income Statements, [Line Items]
Dividends from subsidiaries	[2]										2,393		1,483	962
Management and service fees from subsidiaries	[2]										260		272	292
Net investment income											22		13	11
Interest from subsidiaries	[2]										6		6	7
Realized investment gains (losses)											86		45	10
Change in fair value on the cross-currency interest rate swaps											(53)		314	274
Other income											0		(11)	1
Total revenues											2,714		2,122	1,557
Interest expense											231		243	208
Other operating expenses											321		88	79
Total operating expenses											552		331	287
Earnings before income taxes											2,162		1,791	1,270
Current tax expense (benefit)											2		1	0
Deferred tax expense (benefit)											(82)		120	98
Total income tax expense											(80)		121	98
Earnings before equity in undistributed earnings of subsidiaries											2,242		1,670	1,172
Equity in undistributed earnings of subsidiaries	[2]										291		1,281	1,986
Net earnings											2,533		$ 2,951	$ 3,158
8.50% senior notes due May 2019
Condensed Income Statements, [Line Items]
Expense on extinguishment of debt, make-whole premium		$ 230									$ 230

[1] Includes expense of $230 for the make-whole payment associated with the early extinguishment of debt

[2] Eliminated in consolidation