Economic Maturities of Investments in Perpetual Securities (Detail) (USD $) In Millions	Sep. 30, 2011
Aflac Japan
Investments Classified by Contractual Maturity Date [Line Items]
Due in one year or less	$ 458
Due after one year through five years	1,707
Due after five years through 10 years	749
Due after 10 years	4,413
Total perpetual securities available for sale	7,327
Due in one year or less	524
Due after one year through five years	1,611
Due after five years through 10 years	691
Due after 10 years	3,539
Total perpetual securities available for sale	6,365
Aflac U.S.
Investments Classified by Contractual Maturity Date [Line Items]
Due in one year or less	0
Due after one year through five years	5
Due after five years through 10 years	0
Due after 10 years	172
Total perpetual securities available for sale	177
Due in one year or less	0
Due after one year through five years	5
Due after five years through 10 years	0
Due after 10 years	160
Total perpetual securities available for sale	$ 165

This item represents perpetual securities, at cost, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments, as defined), and fair value hedge accounting adjustments, if any, which are expected to mature after five years and through ten years from the balance sheet date and which are categorized neither as held-to-maturity nor trading securities.

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This item represents the fair value of perpetual securities which are expected to mature after five years and through ten years from the balance sheet date and which are categorized neither as held-to-maturity nor trading securities.

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This item represents perpetual securities, at cost, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments, as defined), and fair value hedge accounting adjustments, if any, which are expected to mature after one year and through five years from the balance sheet date and which are categorized neither as held-to-maturity nor trading securities.

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This item represents the fair value of perpetual securities which are expected to mature after one year and through five years from the balance sheet date and which are categorized neither as held-to-maturity nor trading securities.

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This item represents perpetual securities, at cost, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments, as defined), and fair value hedge accounting adjustments, if any, which are expected to mature after ten years from the balance sheet date and which are categorized neither as held-to-maturity nor trading securities.

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Available for sale Securities, Perpetual Securities, Economic Maturities, after Ten Years, Fair Value

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This item represents the total of all perpetual securities grouped by economic maturity dates, at cost, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments, as defined), and fair value hedge accounting adjustments, if any, which are categorized neither as held-to-maturity nor trading securities.

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This item represents the total of all perpetual securities grouped by economic maturity dates, at fair value, which are categorized neither as held-to-maturity nor trading securities.

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This item represents perpetual securities, at cost, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments, as defined), and fair value hedge accounting adjustments, if any, which are expected to mature within one year of the balance sheet date and which are categorized neither as held-to-maturity nor trading securities.

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This item represents the fair value of perpetual securities which are expected to mature within one year of the balance sheet date and which are categorized neither as held-to-maturity nor trading securities.

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Investments Classified by Contractual Maturity Date [Line Items]

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