Summary of Business and Significant Accounting Policies (Income Taxes) (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Apr. 30, 2011	Apr. 30, 2010
Summary of Business and Significant Accounting Policies
Income tax benefit recognized from stock compensation expense	$ 16.5	$ 9.7
Effective income tax rate	32.00%	38.00%
U.S. federal statutory rate	35.00%	35.00%

Summary of Business and Significant Accounting Policies.

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 47

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph h
-Subparagraph 2
-Article 4

+ Details

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- Definition

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 shall be the regular tax rate if there are alternative tax systems.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 47

+ Details

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- Definition

The total recognized tax benefit related to compensation cost for share-based payment arrangements recognized in income during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph g(1)

+ Details

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