Business Developments, Risks And Uncertainties, And Liquidity (Change In Credit Spreads (Asset/Liability Products Business)) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012
200 Basis Point Decrease [Member]
Investment Holdings [Line Items]
Estimated change in fair value	$ 210
50 Basis Point Decrease [Member]
Investment Holdings [Line Items]
Estimated change in fair value	67
50 Basis Point Increase [Member]
Investment Holdings [Line Items]
Estimated change in fair value	(64)
200 Basis Point Increase [Member]
Investment Holdings [Line Items]
Estimated change in fair value	$ (233)