Operations by Segment - Revenues and Pretax Earnings (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums	$ 5,324	$ 5,210	$ 4,956	$ 4,872	$ 4,785	$ 4,607	$ 4,333	$ 4,348	$ 20,362	$ 18,073	$ 16,621
Net Investment Income	858	843	784	794	789	765	727	726	3,280	3,007	2,765
Other income	20	17	16	30	15	13	9	37	81	74	80
Realized investment gains (losses)									(1,552)	(422)	(1,212)
Pretax operating earnings									4,544	4,007	3,435
Gain on extinguishment of debt									0	0	16
Other									0	0	(4)
Earnings before income taxes	834	1,105	453	600	667	1,055	889	974	2,992	3,585	2,235
Income taxes applicable to pretax operating earnings									1,571	1,389	1,158
Effect of foreign currency translation on operating earnings									170	92	124
Total revenues	5,979	5,987	5,088	5,117	5,294	5,394	4,980	5,065	22,171	20,732	18,254
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									15,619	13,487	12,178
Net Investment Income									2,688	2,453	2,265
Other income									46	37	43
Total business segment revenues									18,353	15,977	14,486
Pretax operating earnings									3,858	3,283	2,800
Aflac Japan | Cancer
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									7,541	6,852	6,406
Aflac Japan | Medical and Other Health
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									5,158	4,574	4,110
Aflac Japan | Life insurance
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									2,920	2,061	1,662
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									4,743	4,586	4,444
Net Investment Income									588	549	499
Other income									10	11	10
Total business segment revenues									5,341	5,146	4,953
Pretax operating earnings									917	924	776
Aflac U.S. | Cancer
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									1,258	1,239	1,245
Aflac U.S. | Life insurance
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									230	217	198
Aflac U.S. | Accident and Disability
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									2,194	2,104	2,012
Aflac U.S. | Other Health
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									1,061	1,026	989
Other business segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total business segment revenues									54	51	51
Pretax operating earnings									1	(3)	0
Total Business Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total business segment revenues									23,748	21,174	19,490
Pretax operating earnings									4,776	4,204	3,576
Corporate
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues									241	217	137
Intercompany eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues									(266)	(237)	(161)
Interest Expense, noninsurance operations
Segment Reporting, Revenue Reconciling Item [Line Items]
Pretax operating earnings									(168)	(140)	(73)
Corporate and eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Pretax operating earnings									$ (64)	$ (57)	$ (68)