Schedule II - Aflac Incorporated (Parent Only) - Condensed Balance Sheet (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Investments and cash:
Other investments	$ 171		$ 463
Cash and cash equivalents	4,658		2,543		2,041	2,249
Total investments and cash	107,341		108,459
Other assets	2,120	[1]	1,606	[1]
Total assets	119,767		121,307		131,094
Liabilities:
Income taxes	5,293		3,718
Notes payable	5,268		4,891
Other liabilities	4,719	[2]	2,850	[2]
Total liabilities	101,420		106,687
Shareholders' equity:
Common stock of $.10 par value. In thousands: authorized 1,900,000 shares in 2014 and 2013; issued 668,132 shares in 2014 and 667,046 shares in 2013	67		67
Additional paid-in capital	1,711		1,644
Retained earnings	22,156		19,885
Accumulated other comprehensive income (loss):
Unrealized foreign currency translation gains (losses)	(2,541)		(1,505)
Unrealized gains (losses) on investment securities	4,672		1,035
Unrealized gains (losses) on derivatives	(26)		(12)
Pension liability adjustment	(126)		(81)
Treasury stock, at average cost	(7,566)		(6,413)
Total shareholders' equity	18,347		14,620		15,978
Total liabilities and shareholders' equity	119,767		121,307
Parent Company
Investments and cash:
Fixed maturity securities available for sale, at fair value (amortized cost $419 in 2014 and $322 in 2013)	437		332
Investments in subsidiaries	21,430	[3]	17,678	[3]
Other investments	24		313
Cash and cash equivalents	1,638		1,081		830	385
Total investments and cash	23,529		19,404
Due from subsidiaries	116	[3]	128	[3]
Other assets	766		464
Total assets	24,411		19,996
Liabilities:
Income taxes	6		(120)
Employee benefit plans	282		246
Notes payable	5,285		4,910
Other liabilities	491		340
Total liabilities	6,064		5,376
Shareholders' equity:
Common stock of $.10 par value. In thousands: authorized 1,900,000 shares in 2014 and 2013; issued 668,132 shares in 2014 and 667,046 shares in 2013	67		67
Additional paid-in capital	1,711		1,644
Retained earnings	22,156		19,885
Accumulated other comprehensive income (loss):
Unrealized foreign currency translation gains (losses)	(2,541)		(1,505)
Unrealized gains (losses) on investment securities	4,672		1,035
Unrealized gains (losses) on derivatives	(26)		(12)
Pension liability adjustment	(126)		(81)
Treasury stock, at average cost	(7,566)		(6,413)
Total shareholders' equity	18,347		14,620
Total liabilities and shareholders' equity	$ 24,411		$ 19,996

[1] Includes $106 in 2014 and 2013 of derivatives from consolidated variable interest entities

[2] Includes $318 in 2014 and $207 in 2013 of derivatives from consolidated variable interest entities

[3] Eliminated in consolidation