Schedule II - Aflac Incorporated (Parent Only) - Summary of Notes Payable (Detail) (Parent Company, USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 3,345		$ 3,098
8.50% senior notes due May 2019
Condensed Financial Statements, Captions [Line Items]
Notes payable	850		850
6.45% senior notes due August 2040
Condensed Financial Statements, Captions [Line Items]
Notes payable	448	[1]	448	[1]
6.90% senior notes due December 2039
Condensed Financial Statements, Captions [Line Items]
Notes payable	396	[2]	396	[2]
3.45% senior notes due August 2015
Condensed Financial Statements, Captions [Line Items]
Notes payable	300		300
1.52% yen-denominated Uridashi notes paid September 2011
Condensed Financial Statements, Captions [Line Items]
Notes payable	0		184
2.26% yen-denominated Uridashi notes due September 2016
Condensed Financial Statements, Captions [Line Items]
Notes payable	129		123
Variable interest rate yen-denominated Uridashi notes paid September 2011
Condensed Financial Statements, Captions [Line Items]
Notes payable	0		245
1.47% yen-denominated Samurai notes due July 2014
Condensed Financial Statements, Captions [Line Items]
Notes payable	369		0
1.87% yen-denominated Samurai notes due June 2012
Condensed Financial Statements, Captions [Line Items]
Notes payable	386		368
1.84% yen-denominated Samurai notes due July 2016
Condensed Financial Statements, Captions [Line Items]
Notes payable	203		0
Variable interest rate yen-denominated Samurai notes due July 2014
Condensed Financial Statements, Captions [Line Items]
Notes payable	71		0
3.60% yen-denominated loan due July 2015
Condensed Financial Statements, Captions [Line Items]
Notes payable	129		123
3.00% yen-denominated loan due August 2015
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 64		$ 61

[1] $450 issuance net of a $2 underwriting discount that is being amortized over the life of the notes

[2] $400 issuance net of a $4 underwriting discount that is being amortized over the life of the notes