Short -Term Investments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Investments
Cost Basis	$ 67,983	$ 102,936
Unrealized Gains	3	26
Unrealized Losses	(13)	(128)
Fair Value	67,973	102,834
Short-term investments [Member]
Investments
Cost Basis	65,296	100,129
Unrealized Gains	3	26
Unrealized Losses	(13)	(128)
Fair Value	65,286	100,027
Short-term investments [Member] \| Money Market Mutual Funds [Member]
Investments
Cost Basis	29,816	47,140
Unrealized Gains
Unrealized Losses
Fair Value	29,816	47,140
Short-term investments [Member] \| Commercial Paper [Member]
Investments
Cost Basis	5,494	15,690
Unrealized Gains	1
Unrealized Losses	(2)	(12)
Fair Value	5,493	15,678
Short-term investments [Member] \| Corporate bonds and notes [Member]
Investments
Cost Basis	29,986	37,299
Unrealized Gains	2	26
Unrealized Losses	(11)	(116)
Fair Value	29,977	37,209
Deferred compensation plan assets included in other assets [Member]
Investments
Cost Basis	2,687	2,807
Unrealized Gains
Unrealized Losses
Fair Value	$ 2,687	$ 2,807

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+ Details

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.

+ References+ Details

- 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+ Details