STATUTORY ACCOUNTING AND DIVIDEND RESTRICTIONS - Profit Remittances by Aflac Japan (Detail) $ in Millions, ¥ in Billions	12 Months Ended
Dec. 31, 2020 USD ($)	Dec. 31, 2020 JPY (¥)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 JPY (¥)	Dec. 31, 2018 USD ($)	Dec. 31, 2018 JPY (¥)
Insurance [Abstract]
Profit remittances	$ 1,215	¥ 129.8	$ 2,070	¥ 225.2	$ 808	¥ 89.7

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