Note 4. Fair Value Measurements (Detail) - Financial Assets Measured at Fair Value (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Cash equivalents
Cash equivalents	$ 21,616	$ 56,339
Short-term investments
Short-term investments	151,817	126,976
Commercial Paper [Member] \| Fair Value, Inputs, Level 2 [Member]
Short-term investments
Short-term investments	4,496	4,850
Commercial Paper [Member]
Short-term investments
Short-term investments	4,496	4,850
Muncipal Bonds [Member] \| Fair Value, Inputs, Level 2 [Member]
Short-term investments
Short-term investments	122,174	65,675
Muncipal Bonds [Member]
Short-term investments
Short-term investments	122,174	65,675
Corporate Bonds [Member] \| Fair Value, Inputs, Level 2 [Member]
Short-term investments
Short-term investments	8,148	6,828
Corporate Bonds [Member]
Short-term investments
Short-term investments	8,148	6,828
US Government Corporations and Agencies Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Short-term investments
Short-term investments	16,999	49,623
US Government Corporations and Agencies Securities [Member]
Short-term investments
Short-term investments	16,999	49,623
Fair Value, Inputs, Level 1 [Member] \| Money Market Funds [Member]
Cash equivalents
Cash equivalents	1,068	21,504
Fair Value, Inputs, Level 1 [Member]
Cash equivalents
Cash equivalents	1,068	21,504
Fair Value, Inputs, Level 2 [Member] \| Commercial Paper [Member]
Cash equivalents
Cash equivalents	18,499	24,405
Fair Value, Inputs, Level 2 [Member] \| Muncipal Bonds [Member]
Cash equivalents
Cash equivalents	2,049	8,385
Fair Value, Inputs, Level 2 [Member] \| Corporate Bonds [Member]
Cash equivalents
Cash equivalents		2,045
Fair Value, Inputs, Level 2 [Member]
Cash equivalents
Cash equivalents	20,548	34,835
Short-term investments
Short-term investments	151,817	126,976
Money Market Funds [Member]
Cash equivalents
Cash equivalents	1,068	21,504
Commercial Paper [Member]
Cash equivalents
Cash equivalents	18,499	24,405
Muncipal Bonds [Member]
Cash equivalents
Cash equivalents	2,049	8,385
Corporate Bonds [Member]
Cash equivalents
Cash equivalents		$ 2,045

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.

+ References+ Details