BUSINESS SEGMENT AND FOREIGN INFORMATION - Operations by Segment - Pretax Earnings (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings									$ 4,658	$ 4,502	$ 3,983
Realized investment gains (losses)									(349)	(1,552)	(422)
Other non-operating income (loss)									(7)	0	0
Earnings before income taxes	880	1,480	741	1,202	822	1,092	444	591	4,302	2,950	3,561
Income taxes applicable to pretax operating earnings									1,561	1,556	1,381
Effect of foreign currency translation on operating earnings									8	169	90
Aflac Japan
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings									3,904	3,829	3,260
Aflac U.S.
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings									997	904	922
Other business segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings									(3)	1	(2)
Total Business Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings									4,898	4,734	4,180
Interest expense, noninsurance operations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings									(184)	(168)	(140)
Corporate and eliminations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings									$ (56)	$ (64)	$ (57)