Schedule II - Aflac Incorporated (Parent Only) - Condensed Balance Sheet (Parenthetical) (Detail) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Common stock, par value (in dollars per share)	$ 0.1	$ 0.1
Common stock, shares authorized (in shares)	1,900,000	1,900,000
Common stock, shares issued (in shares)	665,239	663,639
Parent Company
Condensed Financial Statements, Captions [Line Items]
Securities available for sale, fixed maturities, amortized cost	$ 131	$ 120
Common stock, par value (in dollars per share)	$ 0.10	$ 0.1
Common stock, shares authorized (in shares)	1,900,000	1,900,000
Common stock, shares issued (in shares)	665,239	663,639