Schedule II - Aflac Incorporated (Parent Only) - Summary of Notes Payable (Detail)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	May 31, 2009 8.50% senior notes due May 2019 USD ($)	Dec. 31, 2012 6.45% senior notes due August 2040 USD ($)	Aug. 31, 2010 6.45% senior notes due August 2040 USD ($)	Dec. 31, 2012 6.90% senior notes due December 2039 USD ($)	Dec. 31, 2009 6.90% senior notes due December 2039 USD ($)	Aug. 31, 2010 3.45% senior notes due August 2015 USD ($)	Dec. 31, 2012 2.65% senior notes due February 2017 USD ($)	Jul. 31, 2012 2.65% senior notes due February 2017 USD ($)	Feb. 29, 2012 2.65% senior notes due February 2017 USD ($)	Dec. 31, 2012 4.00% senior notes due February 2022 USD ($)	Feb. 29, 2012 4.00% senior notes due February 2022 USD ($)	Dec. 31, 2012 5.50% subordinated notes due September 2052 USD ($)	Oct. 31, 2012 5.50% subordinated notes due September 2052 USD ($)	Sep. 30, 2012 5.50% subordinated notes due September 2052 USD ($)	Dec. 31, 2012 2.26% yen-denominated Uridashi notes due September 2016 JPY (¥)	Dec. 31, 2011 2.26% yen-denominated Uridashi notes due September 2016 JPY (¥)	Sep. 30, 2006 2.26% yen-denominated Uridashi notes due September 2016 JPY (¥)	Dec. 31, 2012 1.47% yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2011 1.47% yen-denominated Samurai notes due July 2014 JPY (¥)	Jul. 31, 2011 1.47% yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2011 1.87% yen-denominated Samurai notes due June 2012 JPY (¥)	Jun. 30, 2007 1.87% yen-denominated Samurai notes due June 2012 JPY (¥)	Dec. 31, 2012 1.84% yen-denominated Samurai notes due July 2016 JPY (¥)	Dec. 31, 2011 1.84% yen-denominated Samurai notes due July 2016 JPY (¥)	Jul. 31, 2011 1.84% yen-denominated Samurai notes due July 2016 JPY (¥)	Dec. 31, 2012 Variable interest rate yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2011 Variable interest rate yen-denominated Samurai notes due July 2014 JPY (¥)	Jul. 31, 2011 Variable interest rate yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2012 3.60% yen-denominated loan due July 2015 JPY (¥)	Dec. 31, 2011 3.60% yen-denominated loan due July 2015 JPY (¥)	Dec. 31, 2012 3.00% yen-denominated loan due August 2015 JPY (¥)	Dec. 31, 2011 3.00% yen-denominated loan due August 2015 JPY (¥)	Dec. 31, 2012 Parent Company USD ($)	Dec. 31, 2011 Parent Company USD ($)	Dec. 31, 2012 Parent Company 8.50% senior notes due May 2019 USD ($)	Dec. 31, 2011 Parent Company 8.50% senior notes due May 2019 USD ($)	Dec. 31, 2012 Parent Company 6.45% senior notes due August 2040 USD ($)		Dec. 31, 2011 Parent Company 6.45% senior notes due August 2040 USD ($)		Dec. 31, 2012 Parent Company 6.90% senior notes due December 2039 USD ($)		Dec. 31, 2011 Parent Company 6.90% senior notes due December 2039 USD ($)		Dec. 31, 2012 Parent Company 3.45% senior notes due August 2015 USD ($)	Dec. 31, 2011 Parent Company 3.45% senior notes due August 2015 USD ($)	Dec. 31, 2012 Parent Company 2.65% senior notes due February 2017 USD ($)		Dec. 31, 2011 Parent Company 2.65% senior notes due February 2017 USD ($)	Dec. 31, 2012 Parent Company 4.00% senior notes due February 2022 USD ($)		Dec. 31, 2011 Parent Company 4.00% senior notes due February 2022 USD ($)	Dec. 31, 2012 Parent Company 5.50% subordinated notes due September 2052 USD ($)	Dec. 31, 2011 Parent Company 5.50% subordinated notes due September 2052 USD ($)	Dec. 31, 2012 Parent Company 2.26% yen-denominated Uridashi notes due September 2016 USD ($)	Dec. 31, 2012 Parent Company 2.26% yen-denominated Uridashi notes due September 2016 JPY (¥)	Dec. 31, 2011 Parent Company 2.26% yen-denominated Uridashi notes due September 2016 USD ($)	Dec. 31, 2011 Parent Company 2.26% yen-denominated Uridashi notes due September 2016 JPY (¥)	Dec. 31, 2012 Parent Company 1.47% yen-denominated Samurai notes due July 2014 USD ($)	Dec. 31, 2012 Parent Company 1.47% yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2011 Parent Company 1.47% yen-denominated Samurai notes due July 2014 USD ($)	Dec. 31, 2011 Parent Company 1.47% yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2012 Parent Company 1.87% yen-denominated Samurai notes due June 2012 USD ($)	Dec. 31, 2012 Parent Company 1.87% yen-denominated Samurai notes due June 2012 JPY (¥)	Dec. 31, 2011 Parent Company 1.87% yen-denominated Samurai notes due June 2012 USD ($)	Dec. 31, 2011 Parent Company 1.87% yen-denominated Samurai notes due June 2012 JPY (¥)	Dec. 31, 2012 Parent Company 1.84% yen-denominated Samurai notes due July 2016 USD ($)	Dec. 31, 2012 Parent Company 1.84% yen-denominated Samurai notes due July 2016 JPY (¥)	Dec. 31, 2011 Parent Company 1.84% yen-denominated Samurai notes due July 2016 USD ($)	Dec. 31, 2011 Parent Company 1.84% yen-denominated Samurai notes due July 2016 JPY (¥)	Dec. 31, 2012 Parent Company Variable interest rate yen-denominated Samurai notes due July 2014 USD ($)	Dec. 31, 2012 Parent Company Variable interest rate yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2011 Parent Company Variable interest rate yen-denominated Samurai notes due July 2014 USD ($)	Dec. 31, 2011 Parent Company Variable interest rate yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2012 Parent Company 3.60% yen-denominated loan due July 2015 USD ($)	Dec. 31, 2012 Parent Company 3.60% yen-denominated loan due July 2015 JPY (¥)	Dec. 31, 2011 Parent Company 3.60% yen-denominated loan due July 2015 USD ($)	Dec. 31, 2011 Parent Company 3.60% yen-denominated loan due July 2015 JPY (¥)	Dec. 31, 2012 Parent Company 3.00% yen-denominated loan due August 2015 USD ($)	Dec. 31, 2012 Parent Company 3.00% yen-denominated loan due August 2015 JPY (¥)	Dec. 31, 2011 Parent Company 3.00% yen-denominated loan due August 2015 USD ($)	Dec. 31, 2011 Parent Company 3.00% yen-denominated loan due August 2015 JPY (¥)
Condensed Financial Statements, Captions [Line Items]
Notes payable	$ 4,343,000,000	$ 3,275,000,000																																	$ 4,367,000,000	$ 3,345,000,000	$ 850,000,000	$ 850,000,000	$ 448,000,000	[1]	$ 448,000,000	[1]	$ 396,000,000	[2]	$ 396,000,000	[2]	$ 300,000,000	$ 300,000,000	$ 657,000,000	[3]	$ 0	$ 349,000,000	[4]	$ 0	$ 500,000,000	$ 0	$ 116,000,000		$ 129,000,000		$ 331,000,000		$ 369,000,000		$ 0		$ 386,000,000		$ 182,000,000		$ 203,000,000		$ 64,000,000		$ 71,000,000		$ 116,000,000		$ 129,000,000		$ 58,000,000		$ 64,000,000
Notes payable, principal amount			850,000,000	450,000,000	450,000,000	400,000,000	400,000,000	300,000,000	650,000,000	250,000,000	400,000,000	350,000,000	350,000,000	450,000,000	50,000,000	450,000,000	8,000,000,000	8,000,000,000	10,000,000,000	28,700,000,000	28,700,000,000	28,700,000,000	26,600,000,000	30,000,000,000	15,800,000,000	15,800,000,000	15,800,000,000	5,500,000,000	5,500,000,000	5,500,000,000	10,000,000,000	10,000,000,000	5,000,000,000	5,000,000,000					450,000,000				400,000,000						650,000,000			350,000,000						10,000,000,000		10,000,000,000		28,700,000,000		28,700,000,000		30,000,000,000		30,000,000,000		15,800,000,000		15,800,000,000		5,500,000,000		5,500,000,000		10,000,000,000		10,000,000,000		5,000,000,000		5,000,000,000
Debt Instrument, Unamortized Discount				2,000,000		4,000,000						1,000,000																											2,000,000				4,000,000									1,000,000
Notes payable, issuance premium									$ 7,000,000																																								$ 7,000,000

[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

[3] )$650 issuance plus $7 of an issuance premium that is being amortized over the life of the notes

[4] $350 issuance net of a $1 underwriting discount that is being amortized over the life of the notes