Schedule II - Aflac Incorporated (Parent Only) - Supplemental Disclosure of Cash Flow Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule of Cash Flow, Supplemental [Line Items]
Interest paid	$ 191	$ 134	$ 61
Shareholder dividend reinvestment
Noncash financing activities:
Treasury stock issued for shareholder dividend reinvestment	23	0	0
Parent Company
Schedule of Cash Flow, Supplemental [Line Items]
Interest paid	163	124	61
Parent Company | Shareholder dividend reinvestment
Noncash financing activities:
Treasury stock issued for shareholder dividend reinvestment	$ 23	$ 0	$ 0