Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair Value, Level 1
Fair Value
Cash and cash equivalents	$ 33,779	$ 186,309
Short-term investments	197,734	95,383
Total cash and cash equivalents and investments	231,513	281,692
Other long-term liabilities	0	0
Total liabilities	0	0
Fair Value, Level 2
Fair Value
Cash and cash equivalents	0	0
Short-term investments	0	0
Total cash and cash equivalents and investments	0	0
Other long-term liabilities	0	0
Total liabilities	0	0
Fair Value, Level 3
Fair Value
Cash and cash equivalents	0	0
Short-term investments	0	0
Total cash and cash equivalents and investments	0	0
Other long-term liabilities	59,276	55,033
Total liabilities	59,276	55,033
Fair Value, Total
Fair Value
Cash and cash equivalents	33,779	186,309
Short-term investments	197,734	95,383
Total cash and cash equivalents and investments	231,513	281,692
Other long-term liabilities	59,276	55,033
Total liabilities	$ 59,276	$ 55,033