Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended			6 Months Ended					3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2009 Accounting Standards Update 2010-26	Jun. 30, 2013 Aflac Japan	Jun. 30, 2012 Aflac Japan	Dec. 31, 2012 Aflac Japan	Dec. 31, 2009 Retained earnings: Accounting Standards Update 2010-26	Dec. 31, 2009 Accumulated Other Comprehensive Income (Loss) Accounting Standards Update 2010-26	Jun. 30, 2013 Dollar denominated investment portfolio Aflac Japan	Jun. 30, 2012 Dollar denominated investment portfolio Aflac Japan	Jun. 30, 2013 Dollar denominated investment portfolio Aflac Japan	Jun. 30, 2012 Dollar denominated investment portfolio Aflac Japan
Significant Accounting Policies [Line Items]
Aflac Japan's percentage of the Company's total revenues						75.00%	77.00%
Percentage of the Company Assets						85.00%		87.00%
Valuation allowance related to deferred tax assets associated with unrealized investment losses	$ 237
Income tax expense (benefit) related to items of other comprehensive income (loss)	(698)	(89)	(756)	222							249	(96)	652	61
Effective income tax rate excluding income tax expense (benefit) related to Aflac Japan's dollar-denominated portfolio											29.70%	8.30%	32.70%	37.50%
Adjustment to shareholders' equity upon adoption of new DAC accounting guidance					$ (458)				$ (391)	$ (67)