DEFERRED POLICY ACQUISITION COSTS AND INSURANCE EXPENSES - Advertising Expense (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Advertising Costs [Line Items]
Advertising expense	$ 229	$ 240	$ 254
Aflac Japan
Advertising Costs [Line Items]
Advertising expense	103	112	127
Aflac U.S.
Advertising Costs [Line Items]
Advertising expense	$ 126	$ 128	$ 127