Cash and Cash Equivalents and Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Available-for-sale Securities [Abstract]
Amortized Cost	$ 82,187	$ 85,441
Gross Unrealized Gains	116	138
Gross Unrealized Losses	(22)	(7)
Fair Market Value	82,281	85,572
Estimated fair value of marketable investments and long-term investments classified by contractual maturity date [Abstract]
Due in less than one year	31,472
Due in 1 to 3 years	36,799
Total	68,271
U.S. Government Notes [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	5,997	4,005
Gross Unrealized Gains	14	4
Gross Unrealized Losses	0	0
Fair Market Value	6,011	4,009
U.S. Government Agencies [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	30,499	24,910
Gross Unrealized Gains	40	48
Gross Unrealized Losses	(13)	0
Fair Market Value	30,526	24,958
Municipal Securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	2,604	4,184
Gross Unrealized Gains	2	23
Gross Unrealized Losses	(4)	(1)
Fair Market Value	2,602	4,206
Commercial Paper [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	9,357	10,515
Gross Unrealized Gains	4	4
Gross Unrealized Losses	0	0
Fair Market Value	9,361	10,519
Corporate Debt Securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	18,570	18,281
Gross Unrealized Gains	56	59
Gross Unrealized Losses	(5)	(6)
Fair Market Value	18,621	18,334
Total Marketable Securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	67,027	61,895
Gross Unrealized Gains	116	138
Gross Unrealized Losses	(22)	(7)
Fair Market Value	67,121	62,026
Cash [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	1,830	2,198
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Market Value	1,830	2,198
Money Market Funds [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	12,180	17,348
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Market Value	12,180	17,348
Commercial Paper [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	1,150	4,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Market Value	1,150	4,000
Cash and Cash Equivalents [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	15,160	23,546
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Market Value	$ 15,160	$ 23,546

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7534914&loc=d3e22054-111558

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 14

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15D

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15E

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15C

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

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

- Definition

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