Income Taxes (Details 3) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2012	Jan. 31, 2011
Net Deferred Tax Liability
Deferred tax liabilities	$ 1,802,841	$ 1,588,086
Deferred tax assets	1,425,131	1,151,019
Less: valuation allowance	(55,330)	(61,744)
Net deferred tax assets	1,369,801	1,089,275
Net deferred tax liability	$ 433,040	$ 498,811

The cumulative amount for all deferred tax liabilities as of the balance sheet date arising from temporary differences between accounting income in accordance with generally accepted accounting principles and tax-basis income that will result in future taxable income exceeding future accounting income.

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The sum of the tax effects as of the balance sheet date of the amounts of all future tax deductions arising from temporary differences between tax basis and generally accepted accounting principles basis recognition of assets, liabilities, revenues and expenses, which can only be deducted for tax purposes when permitted under enacted tax laws ( before the valuation allowance, if any, to reduce such sum amount to net realizable value). Includes any tax benefit realized in deferred tax assets for significant impacts of tax planning strategies.

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- Definition

The sum of the portions of deferred tax assets as of the balance sheet date for which, based on the weight of available evidence, it is more likely than not will not be realized through future reductions of tax-based income.

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- Definition

The cumulative amount of all deferred tax liabilities, which result from applying the applicable tax rate to net taxable temporary differences pertaining to each jurisdiction to which the entity is obligated to pay income tax. A taxable temporary difference is a difference between the tax basis and the carrying amount of an asset or liability in the financial statements prepared in accordance with generally accepted accounting principles that will result in taxable amounts in one or more future periods.

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