Income Taxes - Effective Tax Rates Differing from Prevailing Federal Corporate Income Tax Rates (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Pre-tax from continuing operations [Line Items]
Tax on income from continuing operations at statutory rate	$ (89,777)	$ (659,032)
Tax-exempt interest	(17,795)	(19,872)
Valuation allowance	107,502	685,787
Net addition to (release of) tax reserves		73,850
Other, net	2,919	(3,311)
Tax expense on income from continuing operations	$ 2,849	$ 77,422
Tax on income from continuing operations at statutory rate, tax rate	35.00%	35.00%
Tax-exempt interest, tax rate	6.90%	1.10%
Valuation allowance, tax rate	(41.90%)	(36.40%)
Net addition to (release of) tax reserves, tax rate		(3.90%)
Other, net, tax rate	(1.10%)	0.20%
Tax expense on income from continuing operations, tax rate	(1.10%)	(4.10%)

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A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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The domestic federal statutory tax rate applicable under enacted tax laws to the Company's pretax income from continuing operations for the period. The "statutory" tax rate is the regular tax rate if there are alternative tax systems.

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate attributable to changes in the valuation allowance for deferred tax assets.

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate attributable to all other items not otherwise listed in the existing taxonomy.

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate attributable to income that is exempt from income taxes under enacted tax laws.

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The sum of the differences between the effective income tax rate and domestic federal statutory income tax rate attributable to all income tax settlements during the period.

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The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to pretax Income or Loss from continuing operations; income tax expense or benefit may include interest and penalties on tax uncertainties based on the entity's accounting policy.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to changes in the valuation allowance for deferred tax assets in the period.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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The portion of the difference, between total income tax expense or benefit as reported in the Income Statement for the year/accounting period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations, that is attributable to all other items not otherwise listed in the existing taxonomy.

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The sum of the differences between total income tax expense or benefit as reported in the Income Statement and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to all income tax settlements for the period.

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