v2.4.0.6

Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified	Oct. 31, 2012	Jan. 31, 2012
Summary of marketable securities
Amortized Cost	$ 786,186	$ 100,769
Unrealized Gains	24	2
Unrealized Losses	(8)	(13)
Aggregate Fair Value	354,397	53,634
U.S. agency obligations [Member]
Summary of marketable securities
Amortized Cost	608,658	14,316
Unrealized Gains	22
Unrealized Losses	(5)
Aggregate Fair Value	608,675	14,316
U.S. treasury securities [Member]
Summary of marketable securities
Amortized Cost	70,147
Unrealized Losses	(1)
Aggregate Fair Value	70,146
Commercial paper [Member]
Summary of marketable securities
Amortized Cost	42,697	23,785
Unrealized Gains		1
Unrealized Losses		(1)
Aggregate Fair Value	42,697	23,785
Certificates of deposit [Member]
Summary of marketable securities
Amortized Cost	250
Aggregate Fair Value	250
U.S. corporate securities [Member]
Summary of marketable securities
Amortized Cost	12,026	20,391
Unrealized Gains	2
Unrealized Losses	(1)	(11)
Aggregate Fair Value	12,027	20,380
Municipal securities [Member]
Summary of marketable securities
Amortized Cost	1,361	15,125
Unrealized Gains		1
Unrealized Losses	(1)	(1)
Aggregate Fair Value	1,360	15,125
Money market funds [Member]
Summary of marketable securities
Amortized Cost	51,047	27,152
Aggregate Fair Value	51,047	27,152
Included in cash and cash equivalents [Member]
Summary of marketable securities
Amortized Cost	431,805	47,125
Unrealized Gains	2
Unrealized Losses	(2)	(1)
Aggregate Fair Value	431,805	47,124
Included in marketable securities [Member]
Summary of marketable securities
Amortized Cost	354,381	53,644
Unrealized Gains	22	2
Unrealized Losses	(6)	(12)
Aggregate Fair Value	$ 354,397	$ 53,634

X

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682



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-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 7

-Footnote 2

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 19

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27161-111563



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13, 19

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

This item represents the gross unrealized losses for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References

No definition available.

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- Definition

Total debt and equity financial instruments including: (1) securities held-to-maturity, (2) trading securities, and (3) securities available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27161-111563



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 19

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.4)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878



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