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Income Taxes (Narrative) (Detail) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Non Variable Interest Entities [Line Items]
Federal statutory rate	35.00%	35.00%
Net deferred tax asset	$ 1,300,000,000
Capital loss carryforward		162,000,000
NOL carryforward		1,400,000,000
Non Variable Interest Entities [Member]
Non Variable Interest Entities [Line Items]
Valuation allowance	93,000,000	146,000,000
Valuation Allowance Deferred Tax Asset Change In Amount	$ 53,000,000

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