Schedule II - Aflac Incorporated (Parent Only) - Condensed Statement of Earnings (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Condensed Income Statements, [Line Items]
Net investment income	$ 808	$ 841	$ 843	$ 827	$ 826	$ 821	$ 813	$ 833	$ 3,319		$ 3,293		$ 3,473
Realized investment gains (losses)									215		399		(349)
Total revenues	5,514	5,736	5,838	5,640	5,801	5,886	6,044	6,208	22,728		23,939		25,364
Interest expense									317		293		261
Other operating expenses									178		193		195
Earnings before income taxes	1,075	1,074	1,238	1,104	1,028	1,069	1,358	1,361	4,491		4,816		4,302
Current tax expense (benefit)									1,079		1,236		816
Deferred tax expense (benefit)									461		422		620
Total income tax expense	372	368	428	372	353	367	469	469	1,540		1,658		1,436
Net earnings									2,951		3,158		2,866
Parent Company
Condensed Income Statements, [Line Items]
Dividends from subsidiaries									1,483	[1]	962	[1]	0	[1]
Management and service fees from subsidiaries									272	[1]	292	[1]	249	[1]
Net investment income									13		11		20
Interest from subsidiaries									6	[1]	7	[1]	7	[1]
Realized investment gains (losses)									45		10		1
Change in fair value on the cross-currency interest rate swaps									314		274		154
Other income									(11)		1		(7)
Total revenues									2,122		1,557		424
Interest expense									243		208		184
Other operating expenses									88		79		72
Total operating expenses									331		287		256
Earnings before income taxes									1,791		1,270		168
Current tax expense (benefit)									1		0		1
Deferred tax expense (benefit)									120		98		50
Total income tax expense									121		98		51
Earnings before equity in undistributed earnings of subsidiaries									1,670		1,172		117
Equity in undistributed earnings of subsidiaries									1,281	[1]	1,986	[1]	2,749	[1]
Net earnings									$ 2,951		$ 3,158		$ 2,866

[1] Eliminated in consolidation