Cash Equivalents, Short-term and Long-term Investments (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Cash Equivalents Items [Line Items]
Amortized Cost	$ 219,716	$ 242,474
Gross Unrealized Gains	62	5
Gross Unrealized Losses	(78)	(7)
Estimated Fair Value	219,700	242,472
Classification on Condensed Consolidated Balance Sheets:
Cash equivalents	151,497	205,817
Short-term investments	37,847	34,658
Long-term investments	30,356	1,997
Summary portfolio available-for-sale debt securities, by contractual maturity, amortized cost [Abstract]
Less than one year	37,852	37,162
Greater than one year but less than five years	30,367	1,994
Available for sale securities debt maturities, total cost basis	68,219	39,156
Summary portfolio available-for-sale debt securities, by contractual maturity, fair value [Abstract]
Less than one year	37,847	37,157
Greater than one year but less than five years	30,356	1,997
Available for sale securities debt maturities, total fair value	68,203	39,154
Money Market Funds [Member]
Cash Equivalents Items [Line Items]
Amortized Cost	151,497	203,318
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	151,497	203,318
Corporate Debt Securities [Member]
Cash Equivalents Items [Line Items]
Amortized Cost	49,573	20,437
Gross Unrealized Gains	27	2
Gross Unrealized Losses	(77)	(5)
Estimated Fair Value	49,523	20,434
Commercial Paper [Member]
Cash Equivalents Items [Line Items]
Amortized Cost	6,944	7,998
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	0
Estimated Fair Value	6,943	7,998
US Government Corporations and Agencies Securities [Member]
Cash Equivalents Items [Line Items]
Amortized Cost	6,209	8,727
Gross Unrealized Gains	14	0
Gross Unrealized Losses	0	(2)
Estimated Fair Value	6,223	8,725
US Treasury Securities [Member]
Cash Equivalents Items [Line Items]
Amortized Cost	5,493	1,994
Gross Unrealized Gains	21	3
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 5,514	$ 1,997

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The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle).

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Investments which are intended to be sold in the short term (usually less than one year or the normal operating cycle, whichever is longer) including trading securities, available-for-sale securities, held-to-maturity securities, and other short-term investments not otherwise listed in the existing taxonomy.

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