Short-Term Investments (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule of Available-for-sale Securities [Line Items]
Remaing maturity date in days for marketable securites to be classified as short-term investments	90 days
Amortized Cost	$ 78,246,000	$ 85,226,000
Cash and Cash Equivalents, Amortized Cost	58,944,000	75,326,000	35,987,000	60,895,000
Cash and Cash equivalents, Amortized Cost	78,246,000	85,226,000
Gross Unrealized Gains	1,000	1,000
Gross Unrealized Losses	(2,000)	(4,000)
Fair Value	78,245,000	85,223,000
Cash equivalents	900,000	10,300,000
Obligations of U.S. government agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,013,000	6,219,000
Gross Unrealized Gains	1,000	1,000
Gross Unrealized Losses	(1,000)	(1,000)
Fair Value	9,013,000	6,219,000
Obligations of U.S. corporations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,953,000	2,633,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,000)	(3,000)
Fair Value	6,952,000	2,630,000
Foreign Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,336,000	1,048,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	3,336,000	1,048,000
Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		275,000
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value		275,000
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	905,000	10,035,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	905,000	10,035,000
Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Amortized Cost	58,039,000	65,016,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	58,039,000	65,016,000
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,302,000	9,900,000
Gross Unrealized Gains	1,000	1,000
Gross Unrealized Losses	(2,000)	(4,000)
Fair Value	19,301,000	9,897,000
Amounts Included In Cash And Cash Equivalents [Member] | Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	58,944,000	75,326,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 58,944,000	$ 75,326,000
Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Average remaining contractual maturity of marketable securities	12 months