Rollforward of Deferred Policy Acquisition Costs by Segment (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Deferred policy acquisition costs:
Capitalization	$ 1,680	$ 1,440	$ 1,300
Aflac Japan
Deferred policy acquisition costs:
Balance, beginning of year	6,964	5,846
Capitalization	1,109	929
Amortization	(686)	(597)
Foreign currency translation and other	346	786
Balance, end of year	7,733	6,964
Aflac U.S.
Deferred policy acquisition costs:
Balance, beginning of year	2,770	2,687
Capitalization	567	516
Amortization	(416)	(433)
Foreign currency translation and other	0	0
Balance, end of year	$ 2,921	$ 2,770