Fair Value Of Financial Instruments And Investments (Financial Instruments Measured At Fair Value On Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Carrying Amount	$ 82,565	$ 114,094	$ 238,458	$ 44,791
Total short-term investments, Carrying Amount	48,408	55,694
Total cash and cash equivalents and short-term investments, Carrying Amount	130,973	169,788
Total, Carrying Amount	133,753	172,368
Total cash and cash equivalents and short-term investments, Estimated Fair Value	130,973	169,788
Total, Estimated Fair Value	133,753	172,368
Certificates Of Deposit [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Carrying Amount	2,780	2,580
Total short-term investments, Carrying Amount	48,408	55,694
Total cash and cash equivalents, Estimated Fair Value	2,780	2,580
Total short-term investments, Estimated Fair Value	48,408	55,694
Restricted Cash [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Carrying Amount	2,780	2,580
Total cash and cash equivalents, Estimated Fair Value	2,780	2,580
Level 1 [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents and short-term investments, Estimated Fair Value	130,973	169,788
Total, Estimated Fair Value	133,753	172,368
Level 1 [Member] | Certificates Of Deposit [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Estimated Fair Value	2,780	2,580
Total short-term investments, Estimated Fair Value	48,408	55,694
Level 1 [Member] | Restricted Cash [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Estimated Fair Value	2,780	2,580
Level 2 [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents and short-term investments, Estimated Fair Value
Total, Estimated Fair Value
Level 2 [Member] | Certificates Of Deposit [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Estimated Fair Value
Total short-term investments, Estimated Fair Value
Level 2 [Member] | Restricted Cash [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Estimated Fair Value
Level 3 [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents and short-term investments, Estimated Fair Value
Total, Estimated Fair Value
Level 3 [Member] | Certificates Of Deposit [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Estimated Fair Value
Total short-term investments, Estimated Fair Value
Level 3 [Member] | Restricted Cash [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Estimated Fair Value
Cash And Cash Equivalents [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Carrying Amount	82,565	114,094
Total cash and cash equivalents, Estimated Fair Value	82,565	114,094
Cash And Cash Equivalents [Member] | Cash [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Carrying Amount	12,529	8,680
Total cash and cash equivalents, Estimated Fair Value	12,529	8,680
Cash And Cash Equivalents [Member] | Money Market Funds [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Carrying Amount	70,036	105,414
Total cash and cash equivalents, Estimated Fair Value	70,036	105,414
Cash And Cash Equivalents [Member] | Level 1 [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Estimated Fair Value	82,565	114,094
Cash And Cash Equivalents [Member] | Level 1 [Member] | Cash [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Estimated Fair Value	12,529	8,680
Cash And Cash Equivalents [Member] | Level 1 [Member] | Money Market Funds [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Estimated Fair Value	70,036	105,414
Cash And Cash Equivalents [Member] | Level 2 [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Estimated Fair Value
Cash And Cash Equivalents [Member] | Level 2 [Member] | Cash [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Estimated Fair Value
Cash And Cash Equivalents [Member] | Level 2 [Member] | Money Market Funds [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Estimated Fair Value
Cash And Cash Equivalents [Member] | Level 3 [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Estimated Fair Value
Cash And Cash Equivalents [Member] | Level 3 [Member] | Cash [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Estimated Fair Value
Cash And Cash Equivalents [Member] | Level 3 [Member] | Money Market Funds [Member]
Derivatives, Fair Value [Line Items]
Total cash and cash equivalents, Estimated Fair Value
Total Short-Term Investments [Member]
Derivatives, Fair Value [Line Items]
Total short-term investments, Carrying Amount	48,408	55,694
Total short-term investments, Estimated Fair Value	48,408	55,694
Total Short-Term Investments [Member] | Level 1 [Member]
Derivatives, Fair Value [Line Items]
Total short-term investments, Estimated Fair Value	48,408	55,694
Total Short-Term Investments [Member] | Level 2 [Member]
Derivatives, Fair Value [Line Items]
Total short-term investments, Estimated Fair Value
Total Short-Term Investments [Member] | Level 3 [Member]
Derivatives, Fair Value [Line Items]
Total short-term investments, Estimated Fair Value