Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012
Total assets	$ 1,612,087
Total liabilities	5,083
Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Total assets	333,684
Total liabilities
Significant Other Observable Inputs (Level 2) [Member]
Total assets	1,273,597
Total liabilities	5,083
Significant Unobservable Inputs (Level 3) [Member]
Total assets	4,806
Total liabilities
Prepaid Expenses And Other Current Assets [Member]
Foreign currency derivatives	3,387
Prepaid Expenses And Other Current Assets [Member] \| Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Foreign currency derivatives
Prepaid Expenses And Other Current Assets [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Foreign currency derivatives	3,387
Prepaid Expenses And Other Current Assets [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Foreign currency derivatives
Accrued Expenses And Other Current Liabilities [Member]
Foreign currency derivatives	5,083
Accrued Expenses And Other Current Liabilities [Member] \| Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Foreign currency derivatives
Accrued Expenses And Other Current Liabilities [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Foreign currency derivatives	5,083
Accrued Expenses And Other Current Liabilities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Foreign currency derivatives
Money Market Funds [Member] \| Cash and Cash Equivalents [Member]
Fair value of cash and cash equivalents	136,453
Money Market Funds [Member] \| Cash and Cash Equivalents [Member] \| Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Fair value of cash and cash equivalents	136,453
Money Market Funds [Member] \| Cash and Cash Equivalents [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair value of cash and cash equivalents	0
Money Market Funds [Member] \| Cash and Cash Equivalents [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of cash and cash equivalents	0
Corporate Debt Securities [Member] \| Cash and Cash Equivalents [Member]
Fair value of cash and cash equivalents	51,168
Corporate Debt Securities [Member] \| Cash and Cash Equivalents [Member] \| Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Fair value of cash and cash equivalents	0
Corporate Debt Securities [Member] \| Cash and Cash Equivalents [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair value of cash and cash equivalents	51,168
Corporate Debt Securities [Member] \| Cash and Cash Equivalents [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of cash and cash equivalents	0
Agency Securities [Member] \| Available-For-Sale Securities [Member]
Fair value of investments	661,303
Agency Securities [Member] \| Available-For-Sale Securities [Member] \| Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Fair value of investments
Agency Securities [Member] \| Available-For-Sale Securities [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair value of investments	661,303
Agency Securities [Member] \| Available-For-Sale Securities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of investments
Corporate Securities [Member] \| Available-For-Sale Securities [Member]
Fair value of investments	459,084
Corporate Securities [Member] \| Available-For-Sale Securities [Member] \| Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Fair value of investments
Corporate Securities [Member] \| Available-For-Sale Securities [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair value of investments	454,278
Corporate Securities [Member] \| Available-For-Sale Securities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of investments	4,806
Municipal Securities [Member] \| Cash and Cash Equivalents [Member]
Fair value of cash and cash equivalents	6,029
Municipal Securities [Member] \| Cash and Cash Equivalents [Member] \| Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Fair value of cash and cash equivalents	0
Municipal Securities [Member] \| Cash and Cash Equivalents [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair value of cash and cash equivalents	6,029
Municipal Securities [Member] \| Cash and Cash Equivalents [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of cash and cash equivalents	0
Municipal Securities [Member] \| Available-For-Sale Securities [Member]
Fair value of investments	69,978
Municipal Securities [Member] \| Available-For-Sale Securities [Member] \| Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Fair value of investments
Municipal Securities [Member] \| Available-For-Sale Securities [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair value of investments	69,978
Municipal Securities [Member] \| Available-For-Sale Securities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of investments
Cash [Member] \| Cash and Cash Equivalents [Member]
Fair value of cash and cash equivalents	197,231
Cash [Member] \| Cash and Cash Equivalents [Member] \| Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Fair value of cash and cash equivalents	197,231
Cash [Member] \| Cash and Cash Equivalents [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair value of cash and cash equivalents	0
Cash [Member] \| Cash and Cash Equivalents [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of cash and cash equivalents	0
Government Securities [Member] \| Available-For-Sale Securities [Member]
Fair value of investments	27,454
Government Securities [Member] \| Available-For-Sale Securities [Member] \| Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Fair value of investments
Government Securities [Member] \| Available-For-Sale Securities [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair value of investments	27,454
Government Securities [Member] \| Available-For-Sale Securities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of investments

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

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