Schedule II - Aflac Incorporated (Parent Only) - Supplemental Disclosure of Cash Flow Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Cash Flow, Supplemental [Line Items]
Interest paid	$ 178	$ 164	$ 125
Shareholder dividend reinvestment
Noncash financing activities:
Treasury stock issued for shareholder dividend reinvestment	24	23	0
Parent Company
Schedule of Cash Flow, Supplemental [Line Items]
Interest paid	181	163	124
Parent Company | Shareholder dividend reinvestment
Noncash financing activities:
Treasury stock issued for shareholder dividend reinvestment	$ 25	$ 23	$ 0