Schedule II - Aflac Incorporated (Parent Only) - Condensed Balance Sheet (Detail 1) - USD ($) $ in Millions		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Investments and cash:
Fixed maturity securities available for sale, at fair value (amortized cost $1,209 in 2018 and $1,163 in 2017)	[2],[3]	$ 82,895	[1],[4]	$ 84,313	[5]
Other investments	[6]	7,706		3,402
Cash and cash equivalents		4,337		3,491		$ 4,859	$ 4,350
Total investments and cash		126,243		123,659
Other assets	[7]	2,221		2,023
Total assets		140,406		137,217
Liabilities:
Notes payable		5,765		5,267
Other liabilities	[8]	2,906		2,832
Total liabilities		116,944		112,619
Shareholders' equity:
Common stock of $.10 par value. In thousands: authorized 1,900,000 shares in 2018 and 2017; issued 1,347,540 shares in 2018 and 1,345,762 shares in 2017		135		135
Additional paid-in capital		2,177		2,052
Retained earnings		31,788		29,895
Accumulated other comprehensive income (loss):
Unrealized foreign currency translation gains (losses)		(1,847)		(1,750)
Unrealized gains (losses) on fixed maturity securities	[9]	4,234		5,964
Unrealized gains (losses) on derivatives		(24)		(23)
Pension liability adjustment		(212)		(163)
Treasury stock, at average cost		(12,789)		(11,512)
Total shareholders' equity		23,462		24,598		20,482
Total liabilities and shareholders' equity		140,406		137,217
Parent Company
Investments and cash:
Fixed maturity securities available for sale, at fair value (amortized cost $1,209 in 2018 and $1,163 in 2017)		1,222		1,213
Investments in subsidiaries	[10]	26,230		26,869
Other investments		21		51
Cash and cash equivalents		1,767		1,725		$ 2,037	$ 1,721
Total investments and cash		29,240		29,858
Due from subsidiaries	[10]	98		90
Income taxes receivable		176		121
Other assets		390		366
Total assets		29,904		30,435
Liabilities:
Employee benefit plans		310		341
Notes payable		5,765		5,267
Other liabilities		367		229
Total liabilities		6,442		5,837
Shareholders' equity:
Common stock of $.10 par value. In thousands: authorized 1,900,000 shares in 2018 and 2017; issued 1,347,540 shares in 2018 and 1,345,762 shares in 2017		135		135
Additional paid-in capital		2,177		2,052
Retained earnings		31,788		29,895
Accumulated other comprehensive income (loss):
Unrealized foreign currency translation gains (losses)		(1,847)		(1,750)
Unrealized gains (losses) on fixed maturity securities	[11]	4,234		5,964
Unrealized gains (losses) on derivatives		(24)		(23)
Pension liability adjustment		(212)		(163)
Treasury stock, at average cost		(12,789)		(11,512)
Total shareholders' equity		23,462		24,598
Total liabilities and shareholders' equity		$ 29,904		$ 30,435

[1] Includes perpetual securities ($1,139 at amortized cost and $1,140 at fair value)

[2] Includes perpetual securities

[3] Includes perpetual securities

[4] Includes perpetual securities, categorized in accordance with their respective economic maturities (the expected maturity date created by the combination of features in the financial instrument)

[5] Includes perpetual securities ($1,462 at amortized cost and $1,789 at fair value)

[6] Includes $5,856 in 2018 and $2,341 in 2017 of loan receivables and limited partnerships from consolidated variable interest entities

[7] Includes $182 in 2018 and $151 in 2017 of derivatives from consolidated variable interest entities

[8] Includes $102 in 2018 and $128 in 2017 of derivatives from consolidated variable interest entities

[9] See Note 1 of the Notes to the Consolidated Financial Statements for the adoption of accounting guidance on January 1, 2018 related to financial instruments.

[10] Eliminated in consolidation

[11] See Note 1 of the Notes to the Consolidated Financial Statements for the adoption of accounting guidance on January 1, 2018 related to financial instruments.