Schedule II - Aflac Incorporated (Parent Only) - Condensed Balance Sheet (Parenthetical) (Detail) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Condensed Financial Statements, Captions [Line Items]
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	1,900,000,000	1,900,000,000
Common stock, shares issued	663,639,000	662,660,000
Parent Company
Condensed Financial Statements, Captions [Line Items]
Securities available for sale, Fixed maturities, amortized cost	$ 120	$ 114
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	1,900,000	1,900,000
Common stock, shares issued	663,639	662,660