Securities - Summary of Securities Available-for-Sale Investments (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 116	$ 188
Securities available-for-sale - continuing operations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	116	188
Gross Unrealized Gains		1
Gross Unrealized Losses		(1)
Fair Value	116	188
Securities available-for-sale - discontinued operations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,283	1,694
Gross Unrealized Gains	191	165
Gross Unrealized Losses		(8)
Fair Value	1,474	1,851
Obligations of U.S. states and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1
Fair Value	1
Equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11	10
Fair Value	11	10
Money market funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	104	13
Fair Value	104	13
Subtotal [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	116	187
Gross Unrealized Gains		1
Gross Unrealized Losses		(1)
Fair Value	116	187
Accrued investment income [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		1
Fair Value		1
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		80
Fair Value		80
U.S. government sponsored enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		1
Fair Value		1
U.S. corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		57
Gross Unrealized Gains		1
Gross Unrealized Losses		(1)
Fair Value		57
Foreign debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		26
Fair Value		$ 26

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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+ Details

- Definition

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

+ References+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details