Schedule II - Aflac Incorporated (Parent Only) - Condensed Balance Sheet (Detail 1) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments and cash:
Fixed maturity securities available for sale, at fair value (amortized cost $1,506 in 2019 and $1,209 in 2018)		$ 91,262	$ 82,895
Other investments		1,477	787
Cash and cash equivalents		4,896	4,337	$ 3,491	$ 4,859
Total investments and cash		138,091	126,243
Other assets		2,368	2,221
Total assets		152,768	140,406
Liabilities:
Notes payable		6,408	5,765
Other liabilities		3,440	2,906
Total liabilities		123,809	116,944
Shareholders' equity:
Common stock of $.10 par value. In thousands: authorized 1,900,000 shares in 2019 and 2018; issued 1,349,309 shares in 2019 and 1,347,540 shares in 2018		135	135
Additional paid-in capital		2,313	2,177
Retained earnings		34,291	31,788
Accumulated other comprehensive income (loss):
Unrealized foreign currency translation gains (losses)		(1,623)	(1,847)
Unrealized gains (losses) on fixed maturity securities		8,548	4,234
Unrealized gains (losses) on derivatives		(33)	(24)
Pension liability adjustment		(277)	(212)
Treasury stock, at average cost		(14,395)	(12,789)
Total shareholders' equity		28,959	23,462	24,598	20,482
Total liabilities and shareholders' equity		152,768	140,406
Parent Company
Investments and cash:
Fixed maturity securities available for sale, at fair value (amortized cost $1,506 in 2019 and $1,209 in 2018)		1,567	1,222
Investments in subsidiaries	[1]	30,744	26,230
Other investments		36	21
Cash and cash equivalents		2,508	1,767	$ 1,725	$ 2,037
Total investments and cash		34,855	29,240
Due from subsidiaries	[1]	170	98
Income taxes receivable		337	176
Other assets		405	390
Total assets		35,767	29,904
Liabilities:
Employee benefit plans		323	310
Notes payable		6,136	5,765
Other liabilities		349	367
Total liabilities		6,808	6,442
Shareholders' equity:
Common stock of $.10 par value. In thousands: authorized 1,900,000 shares in 2019 and 2018; issued 1,349,309 shares in 2019 and 1,347,540 shares in 2018		135	135
Additional paid-in capital		2,313	2,177
Retained earnings		34,291	31,788
Accumulated other comprehensive income (loss):
Unrealized foreign currency translation gains (losses)		(1,623)	(1,847)
Unrealized gains (losses) on fixed maturity securities		8,548	4,234
Unrealized gains (losses) on derivatives		(33)	(24)
Pension liability adjustment		(277)	(212)
Treasury stock, at average cost		(14,395)	(12,789)
Total shareholders' equity		28,959	23,462
Total liabilities and shareholders' equity		$ 35,767	$ 29,904

[1] Eliminated in consolidation