Debt (Details 1) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jul. 02, 2012
Additional information regarding convertible notes
Principal amount of the liability component	$ 91,875	$ 91,875	$ 91,900
Less unamortized debt discount		(5,450)
Net carrying amount of liability component	91,875	86,425
Carrying amount of the equity component	23,360	23,360
Remaining amortization period of discount	0 months	6 months
Conversion price	$ 21.78	$ 21.78
Effective interest rate on liability component	18.41%	18.41%
If-converted value in excess of principal amount	$ 34,681	$ 3,454
If-converted number of shares to be issued	1,156	153