FAIR VALUE MEASUREMENTS - Estimated Effect of Potential Changes in Interest Rates, Credit Spreads and Interest Rate Volatility on Fair Values of Securities Priced by Discounted Cash Flow Pricing Model (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012
Interest Rates
Discounted Cash Flow Pricing Model, by Assumption [Line Items]
Factor Change	0.50%
Credit Spreads
Discounted Cash Flow Pricing Model, by Assumption [Line Items]
Factor Change	0.50%
Interest Rate Volatility
Discounted Cash Flow Pricing Model, by Assumption [Line Items]
Factor Change	50.00%
Available-for-Sale Fixed Maturity and Perpetual Securities | Interest Rates | Upward Movements
Discounted Cash Flow Pricing Model, by Assumption [Line Items]
Factor Change	0.50%
Change in fair value	(978)
Available-for-Sale Fixed Maturity and Perpetual Securities | Interest Rates | Downward Movements
Discounted Cash Flow Pricing Model, by Assumption [Line Items]
Factor Change	(0.50%)
Change in fair value	999
Available-for-Sale Fixed Maturity and Perpetual Securities | Credit Spreads | Upward Movements
Discounted Cash Flow Pricing Model, by Assumption [Line Items]
Factor Change	0.50%
Change in fair value	(975)
Available-for-Sale Fixed Maturity and Perpetual Securities | Credit Spreads | Downward Movements
Discounted Cash Flow Pricing Model, by Assumption [Line Items]
Factor Change	(0.50%)
Change in fair value	1,011
Available-for-Sale Fixed Maturity and Perpetual Securities | Interest Rate Volatility | Upward Movements
Discounted Cash Flow Pricing Model, by Assumption [Line Items]
Factor Change	50.00%
Change in fair value	(36)
Available-for-Sale Fixed Maturity and Perpetual Securities | Interest Rate Volatility | Downward Movements
Discounted Cash Flow Pricing Model, by Assumption [Line Items]
Factor Change	(50.00%)
Change in fair value	1
Held-to-maturity Securities | Interest Rates | Upward Movements
Discounted Cash Flow Pricing Model, by Assumption [Line Items]
Factor Change	0.50%
Change in fair value	(1,488)
Held-to-maturity Securities | Interest Rates | Downward Movements
Discounted Cash Flow Pricing Model, by Assumption [Line Items]
Factor Change	(0.50%)
Change in fair value	1,314
Held-to-maturity Securities | Credit Spreads | Upward Movements
Discounted Cash Flow Pricing Model, by Assumption [Line Items]
Factor Change	0.50%
Change in fair value	(1,379)
Held-to-maturity Securities | Credit Spreads | Downward Movements
Discounted Cash Flow Pricing Model, by Assumption [Line Items]
Factor Change	(0.50%)
Change in fair value	1,380
Held-to-maturity Securities | Interest Rate Volatility | Upward Movements
Discounted Cash Flow Pricing Model, by Assumption [Line Items]
Factor Change	50.00%
Change in fair value	(132)
Held-to-maturity Securities | Interest Rate Volatility | Downward Movements
Discounted Cash Flow Pricing Model, by Assumption [Line Items]
Factor Change	(50.00%)
Change in fair value	167