BUSINESS SEGMENT AND FOREIGN INFORMATION - Information on Transfers of Funds from Aflac Japan (Detail) $ in Millions, ¥ in Billions	12 Months Ended
Dec. 31, 2019 USD ($)	Dec. 31, 2019 JPY (¥)	Dec. 31, 2018 USD ($)	Dec. 31, 2018 JPY (¥)	Dec. 31, 2017 USD ($)	Dec. 31, 2017 JPY (¥)
Segment Reporting [Abstract]
Management fees	$ 75		$ 136		$ 93
Allocated expenses	4		24		109
Profit remittances	2,070	¥ 225.2	808	¥ 89.7	1,150	¥ 129.3
Total transfers from Aflac Japan	$ 2,149		$ 968		$ 1,352

Amount of foreign earnings repatriated from subsidiaries outside the country of domicile.

No definition available.

Name:	us-gaap_ForeignEarningsRepatriated
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration