Fair Value of Financial Instruments (Details) (USD $) In Thousands	Oct. 01, 2011	Dec. 31, 2010
Assets:
Cash	$ 22,579	$ 72,422
Cash equivalents	91,101	120,042
Short-term—marketable securities	33,544	31,192
Non-qualified Deferred Compensation Plan	3,281	2,971
Total	150,505	226,627
Liabilities:
Earnout Payment Liability	769	1,365
Non-qualified Deferred Compensation Plan	3,281	2,971
Total	4,050	4,336
Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Cash	0	0
Cash equivalents	50,930	120,042
Short-term—marketable securities	6,232	4,822
Non-Qualified Deferred Compensation Plan	3,281	2,971
Total	60,443	127,835
Liabilities:
Earnout Payment Liability	0	0
Non-Qualified Deferred Compensation Plan	3,281	2,971
Total	3,281	2,971
Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Cash	0	0
Cash equivalents	40,171	0
Short-term—marketable securities	27,312	26,370
Non-Qualified Deferred Compensation Plan	0	0
Total	67,483	26,370
Liabilities:
Earnout Payment Liability	0	0
Non-Qualified Deferred Compensation Plan	0	0
Total	0	0
Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Cash		0
Cash equivalents	0	0
Short-term—marketable securities	0	0
Non-Qualified Deferred Compensation Plan	0	0
Total	0	0
Liabilities:
Earnout Payment Liability	769	1,365
Non-Qualified Deferred Compensation Plan	0	0
Total	769	1,365
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Cash	22,579	72,422
Cash equivalents	91,101	120,042
Short-term—marketable securities	33,544	31,192
Non-Qualified Deferred Compensation Plan	3,281	2,971
Total	150,505	226,627
Liabilities:
Earnout Payment Liability	769	1,365
Non-Qualified Deferred Compensation Plan	3,281	2,971
Total	$ 4,050	$ 4,336