Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Income Tax [Line Items]
U. S. federal statutory income tax rate	35.00%
Non-cash charge for state deferred income taxes		$ 1.0

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 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, that is attributable to changes in the income tax rates under enacted tax laws in the period.

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