Fair Value Measurements (Assets Measured At Fair Value) (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	$ 35,317	$ 11,051
U.S. Government And Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	3,855	3,858
Corporate Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	20,810	5,122
Other Fixed Income Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	418	545
International Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	10,234	1,526
Quoted Market Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments
Quoted Market Prices in Active Markets for Identical Assets (Level 1) [Member] \| U.S. Government And Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments
Quoted Market Prices in Active Markets for Identical Assets (Level 1) [Member] \| Corporate Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments
Quoted Market Prices in Active Markets for Identical Assets (Level 1) [Member] \| Other Fixed Income Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments
Quoted Market Prices in Active Markets for Identical Assets (Level 1) [Member] \| International Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	35,317	11,051
Significant Other Observable Inputs (Level 2) [Member] \| U.S. Government And Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	3,855	3,858
Significant Other Observable Inputs (Level 2) [Member] \| Corporate Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	20,810	5,122
Significant Other Observable Inputs (Level 2) [Member] \| Other Fixed Income Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	418	545
Significant Other Observable Inputs (Level 2) [Member] \| International Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	10,234	1,526
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments
Significant Unobservable Inputs (Level 3) [Member] \| U.S. Government And Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments
Significant Unobservable Inputs (Level 3) [Member] \| Corporate Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments
Significant Unobservable Inputs (Level 3) [Member] \| Other Fixed Income Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments
Significant Unobservable Inputs (Level 3) [Member] \| International Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term 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 represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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