Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Fair Value, Level 1
Fair Value
Cash and cash equivalents	$ 34,248	$ 30,423
Short-term investments	162,915	192,785
Total cash and cash equivalents and investments	197,163	223,208
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	31,184	29,920
Total liabilities	31,184	29,920
Fair Value, Total
Fair Value
Cash and cash equivalents	34,248	30,423
Short-term investments	162,915	192,785
Total cash and cash equivalents and investments	197,163	223,208
Other long-term liabilities	31,184	29,920
Total liabilities	$ 31,184	$ 29,920