SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Summary of Signficant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2009
Significant Accounting Policies [Line Items]
Income tax expense (benefit) related to items of other comprehensive income (loss)	$ 1,803	$ (581)	$ 1,078
Accounting Standards Update 2010-26
Significant Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets				(458)
Aflac Japan
Significant Accounting Policies [Line Items]
Aflac Japan's percentage of the Company's total revenues	72.00%	74.00%	77.00%
Percentage of the Company assets	82.00%	85.00%
Retained earnings: | Accounting Standards Update 2010-26
Significant Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets				(391)
Accumulated Other Comprehensive Income (Loss) | Accounting Standards Update 2010-26
Significant Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets				(67)
Dollar denominated investment portfolio | Aflac Japan
Significant Accounting Policies [Line Items]
Income tax expense (benefit) related to items of other comprehensive income (loss)		$ 614	$ 492
Effective income tax rate excluding income tax expense (benefit) related to Aflac Japan's dollar-denominated portfolio		31.00%	32.00%