Fair Value Measurements (Schedule Of Financial Instruments) (Details) (USD $)	Apr. 30, 2012		Jan. 31, 2012
Financial Assets:
Financial assets	$ 201,312,000		$ 219,009,000
Derivative assets	1,194,000		1,404,000
Financial Liabilities:
Derivative liabilities	33,000		530,000
Contingent consideration liability for business combination	33,900,000		38,646,000
Financial liabilities	33,933,000		39,176,000
Commercial Paper [Member]
Financial Assets:
Financial assets	9,384,000	[1]	9,383,000	[1]
Money Market Funds [Member]
Financial Assets:
Financial assets	190,734,000	[1]	207,950,000	[1]
Auction Rate Securities [Member]
Financial Assets:
Financial assets			272,000
Commercial Paper And Money Market Funds [Member]
Financial Liabilities:
Cash and cash equivalents	198,000,000		215,200,000
Restricted cash and bank deposits	2,100,000		2,100,000
Quoted Prices to Active Markets For Identical Instruments (Level 1) [Member]
Financial Assets:
Financial assets	190,734,000		207,950,000
Derivative assets	0		0
Financial Liabilities:
Derivative liabilities	0		0
Contingent consideration liability for business combination	0		0
Financial liabilities	0		0
Quoted Prices to Active Markets For Identical Instruments (Level 1) [Member] | Commercial Paper [Member]
Financial Assets:
Financial assets	0	[1]	0	[1]
Quoted Prices to Active Markets For Identical Instruments (Level 1) [Member] | Money Market Funds [Member]
Financial Assets:
Financial assets	190,734,000	[1]	207,950,000	[1]
Quoted Prices to Active Markets For Identical Instruments (Level 1) [Member] | Auction Rate Securities [Member]
Financial Assets:
Financial assets			0
Significant Other Observable Inputs (Level 2) [Member]
Financial Assets:
Financial assets	10,578,000		10,787,000
Derivative assets	1,194,000		1,404,000
Financial Liabilities:
Derivative liabilities	33,000		530,000
Contingent consideration liability for business combination	0		0
Financial liabilities	33,000		530,000
Significant Other Observable Inputs (Level 2) [Member] | Commercial Paper [Member]
Financial Assets:
Financial assets	9,384,000	[1]	9,383,000	[1]
Significant Other Observable Inputs (Level 2) [Member] | Money Market Funds [Member]
Financial Assets:
Financial assets	0	[1]	0	[1]
Significant Other Observable Inputs (Level 2) [Member] | Auction Rate Securities [Member]
Financial Assets:
Financial assets			0
Significant Unobservable Inputs (Level 3) [Member]
Financial Assets:
Financial assets	0		272,000
Derivative assets	0		0
Financial Liabilities:
Derivative liabilities	0		0
Contingent consideration liability for business combination	33,900,000		38,646,000
Financial liabilities	33,900,000		38,646,000
Significant Unobservable Inputs (Level 3) [Member] | Commercial Paper [Member]
Financial Assets:
Financial assets	0	[1]	0	[1]
Significant Unobservable Inputs (Level 3) [Member] | Money Market Funds [Member]
Financial Assets:
Financial assets	0	[1]	0	[1]
Significant Unobservable Inputs (Level 3) [Member] | Auction Rate Securities [Member]
Financial Assets:
Financial assets			$ 272,000

[1] April 30, 2012, $198.0 million of commercial paper and money market funds were classified in “Cash and cash equivalents” and $2.1 million of money market funds were classified in “Restricted cash and bank time deposits” within the condensed consolidated balance sheets. As of January 31, 2012, $215.2 million of commercial paper and money market funds were classified in “Cash and cash equivalents” and $2.1 million of money market funds were classified in “Restricted cash and bank time deposits” within the condensed consolidated balance sheets.