The amount of the valuation allowance recorded for tax benefits that will be credited to shareholders' equity if those tax benefits subsequently become realizable. Examples include 1) adjustments of the opening balance of retained earnings for certain changes in accounting principle or a correction of an error; 2) gains and losses included in comprehensive income but excluded from net income; 3) expenditures that are deductible for income tax purposes that are reported as a reduction of shareholders' equity; 4) expenses for employee stock options recognized differently for financial reporting purposes and income tax purposes; 5) dividends paid on unallocated shares held by an ESOP that are charged to retained earnings and 6) deductible temporary differences that existed at the date of a quasi reorganization.

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The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to continuing operations.

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- Definition

The aggregate amount of other income amounts, the components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating income recognized for the period. Such amounts may include: (a) dividends, (b) interest on securities, (c) profits on securities (net of losses), and (d) miscellaneous other income items.

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- Definition

The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Disclosure [Line Items]
Income tax expense
Increase (decrease) in valuation allowance	22.0	18.1	19.9
Amount of valuation allowance for deferred tax assets allocated to contributed capital	0.4
Other income			0.7
Federal
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	323.8
Federal \| Minimum
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, expiration year	2018
Federal \| Maximum
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, expiration year	2032
Federal \| Research And Development
Income Tax Disclosure [Line Items]
Tax credit carryforward amount	11.2
Federal \| Research And Development \| Minimum
Income Tax Disclosure [Line Items]
Tax credit carryforward amount, expiration year	2018
Federal \| Research And Development \| Maximum
Income Tax Disclosure [Line Items]
Tax credit carryforward amount, expiration year	2032
California State
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	226.2
California State \| Minimum
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, expiration year	2013
California State \| Maximum
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, expiration year	2032
California State \| Research And Development
Income Tax Disclosure [Line Items]
Tax credit carryforward amount	10.5
Foreign
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 28.0