Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Assets:
Cash	$ 63,104	$ 47,502
Cash equivalents	53,549	68,803
Short-term—marketable securities	22,305	46,006
Non-Qualified Deferred Compensation Plan Funds	4,591	3,635
Total	143,549	165,946
Liabilities:
Earnout and milestone payment liability	5,457	890
Non-Qualified Deferred Compensation Plan	4,591	3,635
Total	10,048	4,525
Estimate of Fair Value, Fair Value Disclosure | Fair Value, Measurements, Recurring [Member]
Assets:
Cash, Fair Value Disclosures	63,104	47,502
Cash equivalents	53,549	68,803
Short-term—marketable securities	22,305	46,006
Non-Qualified Deferred Compensation Plan Funds	4,591	3,635
Total	143,549	165,946
Liabilities:
Earnout and milestone payment liability	5,457	890
Non-Qualified Deferred Compensation Plan	4,591	3,635
Total	10,048	4,525
Level 1 | Fair Value, Measurements, Recurring [Member]
Assets:
Cash, Fair Value Disclosures	0	0
Cash equivalents	53,549	40,793
Short-term—marketable securities	4,510	7,501
Non-Qualified Deferred Compensation Plan Funds	4,591	3,635
Total	62,650	51,929
Liabilities:
Earnout and milestone payment liability	0	0
Non-Qualified Deferred Compensation Plan	4,591	3,635
Total	4,591	3,635
Level 2 | Fair Value, Measurements, Recurring [Member]
Assets:
Cash, Fair Value Disclosures	0	0
Cash equivalents	0	28,010
Short-term—marketable securities	17,795	38,505
Non-Qualified Deferred Compensation Plan Funds	0	0
Total	17,795	66,515
Liabilities:
Earnout and milestone payment liability	0	0
Non-Qualified Deferred Compensation Plan	0	0
Total	0	0
Level 3 | Fair Value, Measurements, Recurring [Member]
Assets:
Cash, Fair Value Disclosures
Cash equivalents	0	0
Short-term—marketable securities	0	0
Non-Qualified Deferred Compensation Plan Funds	0	0
Total	0	0
Liabilities:
Earnout and milestone payment liability	5,457	890
Non-Qualified Deferred Compensation Plan	0	0
Total	$ 5,457	$ 890