Cash, Cash Equivalents and Marketable Investments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Cash, cash equivalents and marketable investments [Abstract]
Amortized Cost	$ 83,719	$ 82,972
Gross Unrealized Gains	119	114
Gross Unrealized Losses	(16)	(13)
Fair Market Value	83,822	83,073
Estimated fair value of marketable investments and long-term investments classified by contractual maturity date [Abstract]
Due in less than one year	35,678
Due in 1 to 3 years	37,401
Total	73,079
U.S. Government Notes [Member]
Cash, cash equivalents and marketable investments [Abstract]
Amortized Cost	17,107	10,516
Gross Unrealized Gains	14	11
Gross Unrealized Losses	(9)	(5)
Fair Market Value	17,112	10,522
U.S. Government Agencies [Member]
Cash, cash equivalents and marketable investments [Abstract]
Amortized Cost	21,088	25,823
Gross Unrealized Gains	39	38
Gross Unrealized Losses	(1)	(3)
Fair Market Value	21,126	25,858
Municipal Securities [Member]
Cash, cash equivalents and marketable investments [Abstract]
Amortized Cost	2,042	2,043
Gross Unrealized Gains	4	1
Gross Unrealized Losses	0	(5)
Fair Market Value	2,046	2,039
Commercial Paper [Member]
Cash, cash equivalents and marketable investments [Abstract]
Amortized Cost	14,885	10,239
Gross Unrealized Gains	5	3
Gross Unrealized Losses	0	0
Fair Market Value	14,890	10,242
Corporate Debt Securities [Member]
Cash, cash equivalents and marketable investments [Abstract]
Amortized Cost	17,854	18,109
Gross Unrealized Gains	57	61
Gross Unrealized Losses	(6)	0
Fair Market Value	17,905	18,170
Cash [Member]
Cash, cash equivalents and marketable investments [Abstract]
Amortized Cost	2,757	3,816
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Market Value	2,757	3,816
Money Market Funds [Member]
Cash, cash equivalents and marketable investments [Abstract]
Amortized Cost	5,736	9,926
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Market Value	5,736	9,926
Commercial Paper [Member]
Cash, cash equivalents and marketable investments [Abstract]
Amortized Cost	2,250	2,500
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Market Value	2,250	2,500
Total Cash and Cash Equivalents [Member]
Cash, cash equivalents and marketable investments [Abstract]
Amortized Cost	10,743	16,242
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Market Value	10,743	16,242
Total Marketable Investments [Member]
Cash, cash equivalents and marketable investments [Abstract]
Amortized Cost	72,976	66,730
Gross Unrealized Gains	119	114
Gross Unrealized Losses	(16)	(13)
Fair Market Value	$ 73,079	$ 66,831

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 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