Lease and Rental Expense (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Lease and Rental Expense [Line Items]
Lease and rental expense	$ 82	$ 77	$ 81
Aflac Japan
Lease and Rental Expense [Line Items]
Lease and rental expense	73	68	72
Aflac U.S.
Lease and Rental Expense [Line Items]
Lease and rental expense	8	8	8
All Other
Lease and Rental Expense [Line Items]
Lease and rental expense	$ 1	$ 1	$ 1