INCOME TAXES - Income Tax Effects of Temporary Differences that Gave Rise to Deferred Income Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred income tax liabilities:
Deferred policy acquisition costs	$ 3,404	$ 3,285
Unrealized gains and other basis differences on investments	1,307	2,882
Premiums receivable	149	104
Policy benefit reserves	3,828	3,557
Total deferred income tax liabilities	8,688	9,828
Deferred income tax assets:
Unfunded retirement benefits	8	8
Other accrued expenses	40	141
Policy and contract claims	775	870
Foreign currency loss on Aflac Japan	38	67
Deferred compensation	163	155
Capital loss carryforwards	5	0
Depreciation	119	114
Anticipatory foreign tax credit	4,040	4,504
Deferred foreign tax credit	591	0
Other	150	57
Total deferred income tax assets before valuation allowance	5,929	5,916
Valuation allowance	(738)	(657)
Total deferred income tax assets after valuation allowance	5,191	5,259
Net deferred income tax liability	3,497	4,569
Current income tax liability	523	176
Total income tax liability	$ 4,020	$ 4,745