Depreciation and Other Amortization Expense (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Depreciation and Other Amortization Expenses [Line Items]
Depreciation expense	$ 59		$ 60		$ 60
Other amortization expense	5		22		21
Total depreciation and other amortization expense	$ 64	[1]	$ 82	[1]	$ 81	[1]

[1] Aflac Japan accounted for $51 in 2011, $48 in 2010 and $46 in 2009.