Cash, Cash Equivalents, and Short-Term Investments (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011		Sep. 30, 2011	Dec. 31, 2010
Cash and cash equivalents:
Cash and cash equivalents, Amortized Cost	$ 56,470	$ 96,025
Cash and cash equivalents, Gross Unrealized Gains
Cash and cash equivalents, Gross Unrealized Losses	2
Cash and cash equivalents, Fair Value	56,468	96,025	[1]	13,025	16,410
Short-term investments:
Short-term investments, Amortized Cost	45,081
Short-term investments, Gross Unrealized Gains	132
Short-term investments, Gross Unrealized Losses	1
Short-term investments, Estimated Fair Value	45,212	1,587	[1]
Cash [Member]
Cash and cash equivalents:
Cash and cash equivalents, Amortized Cost	23,766	26,023
Cash and cash equivalents, Gross Unrealized Gains
Cash and cash equivalents, Fair Value	23,766	26,023
Bank deposits [Member]
Cash and cash equivalents:
Cash and cash equivalents, Amortized Cost	12,519	20,000
Cash and cash equivalents, Gross Unrealized Gains
Cash and cash equivalents, Fair Value	12,519	20,000
Short-term investments:
Short-term investments, Amortized Cost	10,063
Short-term investments, Estimated Fair Value	10,063
Commercial paper [Member]
Cash and cash equivalents:
Cash and cash equivalents, Amortized Cost	16,999
Cash and cash equivalents, Gross Unrealized Gains
Cash and cash equivalents, Gross Unrealized Losses	2
Cash and cash equivalents, Fair Value	16,997
Short-term investments:
Short-term investments, Amortized Cost	9,518
Short-term investments, Gross Unrealized Gains	2
Short-term investments, Estimated Fair Value	9,520
Corporate debt obligations [Member]
Short-term investments:
Short-term investments, Amortized Cost	20,830
Short-term investments, Gross Unrealized Gains	47
Short-term investments, Estimated Fair Value	20,877
Money market funds [Member]
Cash and cash equivalents:
Cash and cash equivalents, Amortized Cost	3,186	50,002
Cash and cash equivalents, Gross Unrealized Gains
Cash and cash equivalents, Fair Value	3,186	50,002
US agency securities [Member]
Short-term investments:
Short-term investments, Amortized Cost	2,003
Short-term investments, Gross Unrealized Losses	1
Short-term investments, Estimated Fair Value	2,002
Mutual funds [Member]
Short-term investments:
Short-term investments, Amortized Cost	2,667	1,644
Short-term investments, Gross Unrealized Gains	83
Short-term investments, Gross Unrealized Losses		57
Short-term investments, Estimated Fair Value	$ 2,750	$ 1,587

[1] The Condensed Consolidated Balance Sheet as of December 31, 2011 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.