Estimated Effect of Potential Changes in Interest Rates, Credit Spreads and Interest Rate Volatility on Fair Values of Securities Priced by the Discounted Cash Flow Pricing Model (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2011
Interest Rates | Available-for-Sale Fixed Maturity and Perpetual Securities | Upward Movements
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Factor Change	0.50%
Change in fair value	$ (1,069)
Interest Rates | Available-for-Sale Fixed Maturity and Perpetual Securities | Downward Movements
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Factor Change	(0.50%)
Change in fair value	1,140
Credit Spreads | Available-for-Sale Fixed Maturity and Perpetual Securities | Upward Movements
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Factor Change	0.50%
Change in fair value	(1,054)
Credit Spreads | Available-for-Sale Fixed Maturity and Perpetual Securities | Downward Movements
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Factor Change	(0.50%)
Change in fair value	1,122
Interest Rate Volatility | Available-for-Sale Fixed Maturity and Perpetual Securities | Upward Movements
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Factor Change	50.00%
Change in fair value	(248)
Interest Rate Volatility | Available-for-Sale Fixed Maturity and Perpetual Securities | Downward Movements
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Factor Change	(50.00%)
Change in fair value	33
Interest Rates | Held-to-maturity Securities | Upward Movements
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Factor Change	0.50%
Change in fair value	(1,696)
Interest Rates | Held-to-maturity Securities | Downward Movements
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Factor Change	(0.50%)
Change in fair value	1,747
Credit Spreads | Held-to-maturity Securities | Upward Movements
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Factor Change	0.50%
Change in fair value	(1,557)
Credit Spreads | Held-to-maturity Securities | Downward Movements
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Factor Change	(0.50%)
Change in fair value	1,572
Interest Rate Volatility | Held-to-maturity Securities | Upward Movements
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Factor Change	50.00%
Change in fair value	(385)
Interest Rate Volatility | Held-to-maturity Securities | Downward Movements
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Factor Change	(50.00%)
Change in fair value	$ 357
Interest Rates
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Factor Change	0.50%
Credit Spreads
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Factor Change	0.50%
Interest Rate Volatility
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Factor Change	50.00%