Schedule II - Aflac Incorporated (Parent Only) - Condensed Balance Sheet (Detail 1) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments and cash:
Available for sale, fixed maturity securities		$ 105,882	$ 91,262
Other investments		2,429	1,477
Cash and cash equivalents		5,141	4,896
Total investments and cash		149,753	138,091
Other assets		2,715	2,368
Assets		165,086	152,768
Liabilities:
Notes payable		7,745	6,408
Other Liabilities		3,612	3,440
Total liabilities		131,527	123,809
Shareholders' equity:
Common stock of $.10 par value. In thousands: authorized 1,900,000 shares in 2020 and 2019; issued 1,351,018 shares in 2020 and 1,349,309 shares in 2019		135	135
Additional paid-in capital		2,410	2,313
Retained earnings		37,984	34,291
Accumulated other comprehensive income (loss):
Unrealized foreign currency translation gains (losses)		(1,109)	(1,623)
Unrealized gains (losses) on fixed maturity securities		10,361	8,548
Unrealized gains (losses) on derivatives		(34)	(33)
Pension liability adjustment		(284)	(277)
Treasury stock, at average cost		(15,904)	(14,395)
Total shareholders' equity		33,559	28,959	$ 23,462	$ 24,598
Total liabilities and shareholders' equity		165,086	152,768
Parent Company
Investments and cash:
Available for sale, fixed maturity securities		1,876	1,567
Investments in subsidiaries	[1]	36,217	30,744
Other investments		902	36
Cash and cash equivalents		2,126	2,508	$ 1,767	$ 1,725
Total investments and cash		41,121	34,855
Due from subsidiaries	[1]	253	170
Income taxes receivable		203	337
Other assets		368	405
Assets		41,945	35,767
Liabilities:
Employee benefit plans		340	323
Notes payable		7,456	6,136
Other Liabilities		590	349
Total liabilities		8,386	6,808
Shareholders' equity:
Common stock of $.10 par value. In thousands: authorized 1,900,000 shares in 2020 and 2019; issued 1,351,018 shares in 2020 and 1,349,309 shares in 2019		135	135
Additional paid-in capital		2,410	2,313
Retained earnings		37,984	34,291
Accumulated other comprehensive income (loss):
Unrealized foreign currency translation gains (losses)		(1,109)	(1,623)
Unrealized gains (losses) on fixed maturity securities		10,361	8,548
Unrealized gains (losses) on derivatives		(34)	(33)
Pension liability adjustment		(284)	(277)
Treasury stock, at average cost		(15,904)	(14,395)
Total shareholders' equity		33,559	28,959
Total liabilities and shareholders' equity		$ 41,945	$ 35,767

[1] Eliminated in consolidation