XML 45 R33.htm IDEA: XBRL DOCUMENT v3.20.2
Summary of Significant Accounting Policies - Additional Information (Detail)
$ in Millions, ¥ in Billions
6 Months Ended
Jun. 30, 2020
JPY (¥)
Jun. 30, 2019
USD ($)
Jun. 30, 2020
USD ($)
Apr. 30, 2020
USD ($)
Mar. 31, 2020
JPY (¥)
series
Mar. 31, 2020
USD ($)
series
Jan. 01, 2020
USD ($)
Dec. 31, 2019
USD ($)
Mar. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Significant Accounting Policies [Line Items]                    
Number of Series of Senior Notes Issued Through a U.S. Public Debt Offering | series         4 4        
Cumulative effect of change in accounting principle, net of income taxes   $ 28,241 $ 29,420     $ 26,402   $ 28,959 $ 26,049 $ 23,462
Senior notes                    
Significant Accounting Policies [Line Items]                    
Debt instrument, principal amount | ¥         ¥ 57.0          
3.60% senior notes due April 2030                    
Significant Accounting Policies [Line Items]                    
Debt instrument, principal amount     $ 1,000 $ 1,000            
Aflac Japan                    
Significant Accounting Policies [Line Items]                    
Percentage of the Company's total assets 83.00%   83.00%         84.00%    
Percentage of the Company's total revenues 67.00% 68.00%                
Accounting Standards Update 2019-04                    
Significant Accounting Policies [Line Items]                    
New Accounting Pronouncement Or Change In Accounting Principle Effect Of Adoption Reclassification From Held To Maturity To Available For Sale Debt Securities             $ 6,900      
Unrealized gains (losses) on investment securities                    
Significant Accounting Policies [Line Items]                    
Cumulative effect of change in accounting principle, net of income taxes   $ 6,364 $ 6,750     4,188   $ 6,615 4,481 2,151
Retained earnings                    
Significant Accounting Policies [Line Items]                    
Cumulative effect of change in accounting principle, net of income taxes   $ 33,130 35,204     $ 34,599   34,291 $ 32,513 $ 31,788
100.0 billion yen line of credit                    
Significant Accounting Policies [Line Items]                    
Line of credit facility, maximum borrowing capacity | ¥ ¥ 100.0                  
$1 billion line of credit                    
Significant Accounting Policies [Line Items]                    
Line of credit facility, maximum borrowing capacity     $ 1,000              
Federal Home Loan Bank of Atlanta                    
Significant Accounting Policies [Line Items]                    
Line of credit facility, maximum borrowing capacity       800            
Line of credit facility, capacity designated for short-term liquidity       $ 300            
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2016-13                    
Significant Accounting Policies [Line Items]                    
Cumulative effect of change in accounting principle, net of income taxes [1]               (56)    
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2019-04                    
Significant Accounting Policies [Line Items]                    
Cumulative effect of change in accounting principle, net of income taxes [1]               848    
Cumulative effect, period of adoption, adjustment | Unrealized gains (losses) on investment securities | Accounting Standards Update 2016-13                    
Significant Accounting Policies [Line Items]                    
Cumulative effect of change in accounting principle, net of income taxes [1]               0    
Cumulative effect, period of adoption, adjustment | Unrealized gains (losses) on investment securities | Accounting Standards Update 2019-04                    
Significant Accounting Policies [Line Items]                    
Cumulative effect of change in accounting principle, net of income taxes [1]               848    
Cumulative effect, period of adoption, adjustment | Retained earnings | Accounting Standards Update 2016-13                    
Significant Accounting Policies [Line Items]                    
Cumulative effect of change in accounting principle, net of income taxes [1]               (56)    
Cumulative effect, period of adoption, adjustment | Retained earnings | Accounting Standards Update 2019-04                    
Significant Accounting Policies [Line Items]                    
Cumulative effect of change in accounting principle, net of income taxes [1]               $ 0    
[1] See Note 1 of the Notes to the Consolidated Financial Statements for the adoption of accounting guidance on January 1, 2020.