Significant Accounting Policies (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair value of the Company's investments by type
Amortized Cost	$ 29,178	$ 40,455
Accrued Interest	91	161
Gross Unrealized Gains	43	52
Gross Unrealized Losses	(3)	(12)
Estimated Fair Value	29,309	40,656
Level 2 [Member] \| U.S. Treasury securities [Member]
Fair value of the Company's investments by type
Amortized Cost	1,999	1,998
Accrued Interest	2	2
Gross Unrealized Gains	7	14
Gross Unrealized Losses
Estimated Fair Value	2,008	2,014
Level 2 [Member] \| Obligations of U.S. government and its agencies [Member]
Fair value of the Company's investments by type
Amortized Cost	10,213	5,000
Accrued Interest	12	10
Gross Unrealized Gains
Gross Unrealized Losses	(3)
Estimated Fair Value	10,222	5,010
Level 2 [Member] \| Corporate debt securities [Member]
Fair value of the Company's investments by type
Amortized Cost	6,872	10,924
Accrued Interest	34	80
Gross Unrealized Gains	15	15
Gross Unrealized Losses		(9)
Estimated Fair Value	6,921	11,010
Level 2 [Member] \| Commercial paper [Member]
Fair value of the Company's investments by type
Amortized Cost	1,399	10,939
Accrued Interest
Gross Unrealized Gains		2
Gross Unrealized Losses		(1)
Estimated Fair Value	1,399	10,940
Level 2 [Member] \| Asset-backed securities [Member]
Fair value of the Company's investments by type
Amortized Cost		611
Accrued Interest
Gross Unrealized Gains
Gross Unrealized Losses
Estimated Fair Value		611
Level 2 [Member] \| Certificate of deposit [Member]
Fair value of the Company's investments by type
Amortized Cost	800	801
Accrued Interest		1
Gross Unrealized Gains
Gross Unrealized Losses
Estimated Fair Value	800	802
Level 2 [Member] \| Municipal obligations [Member]
Fair value of the Company's investments by type
Amortized Cost	7,895	10,182
Accrued Interest	43	68
Gross Unrealized Gains	21	21
Gross Unrealized Losses		(2)
Estimated Fair Value	$ 7,959	$ 10,269

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.

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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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- 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.

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