Schedule II - Aflac Incorporated (Parent Only) - Condensed Balance Sheet (Detail) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investments and cash:
Other investments		$ 294	$ 171
Cash and cash equivalents		4,350	4,658	$ 2,543	$ 2,041
Total investments and cash		105,897	107,341
Other assets	[1]	1,988	2,120
Total assets		118,296	119,767		121,307
Liabilities:
Notes payable		4,991	5,268
Other liabilities	[2]	2,665	4,719
Total liabilities		100,588	101,420
Shareholders' equity:
Common stock of $.10 par value. In thousands: authorized 1,900,000 shares in 2015 and 2014; issued 669,723 shares in 2015 and 668,132 shares in 2014		67	67
Additional paid-in capital		1,828	1,711
Retained earnings		24,007	22,156
Accumulated other comprehensive income (loss):
Unrealized foreign currency translation gains (losses)		(2,196)	(2,541)
Unrealized gains (losses) on investment securities		2,986	4,672
Unrealized gains (losses) on derivatives		(26)	(26)
Pension liability adjustment		(139)	(126)
Treasury stock, at average cost		(8,819)	(7,566)
Total shareholders' equity		17,708	18,347	14,620
Total liabilities and shareholders' equity		118,296	119,767
Parent Company
Investments and cash:
Fixed maturity securities available for sale, at fair value (amortized cost $481 in 2015 and $419 in 2014)		493	437
Investments in subsidiaries	[3]	20,500	21,430
Other investments		9	24
Cash and cash equivalents		1,721	1,638	$ 1,081	$ 830
Total investments and cash		22,723	23,529
Due from subsidiaries	[3]	113	116
Other assets		582	766
Total assets		23,418	24,411
Liabilities:
Income taxes		8	6
Employee benefit plans		274	282
Notes payable		5,008	5,285
Other liabilities		420	491
Total liabilities		5,710	6,064
Shareholders' equity:
Common stock of $.10 par value. In thousands: authorized 1,900,000 shares in 2015 and 2014; issued 669,723 shares in 2015 and 668,132 shares in 2014		67	67
Additional paid-in capital		1,828	1,711
Retained earnings		24,007	22,156
Accumulated other comprehensive income (loss):
Unrealized foreign currency translation gains (losses)		(2,196)	(2,541)
Unrealized gains (losses) on investment securities		2,986	4,672
Unrealized gains (losses) on derivatives		(26)	(26)
Pension liability adjustment		(139)	(126)
Treasury stock, at average cost		(8,819)	(7,566)
Total shareholders' equity		17,708	18,347
Total liabilities and shareholders' equity		$ 23,418	$ 24,411

[1] Includes $102 in 2015 and $106 in 2014 of derivatives from consolidated variable interest entities

[2] Includes $293 in 2015 and $318 in 2014 of derivatives from consolidated variable interest entities

[3] Eliminated in consolidation