Employee Stock Benefit Plans (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	6 Months Ended		6 Months Ended
	Jun. 30, 2012 Employee Stock Purchase Plan [Member]	Jun. 30, 2012 Stock Options [Member] Y	May 09, 2012 Stock Options [Member]	Jun. 30, 2012 Restricted Stock Units [Member] Y	Jun. 30, 2012 Equity Based Performance Stock Units [Member]	Jun. 30, 2012 Equity Based Performance Stock Units [Member] Maximum [Member]	Jun. 30, 2012 Equity Based Performance Stock Units [Member] Minimum [Member]	Jun. 30, 2012 1997 ESPP Plan [Member]
Employee Stock Benefit Plans
Percentage of the fair value to determine the price of common stock	85.00%
Minimum period in which vested stock become exercisable		One year		One year
Maximum period in which vested stock become exercisable		Four year		Four year
Maximum period in which vested stock expire		Ten years
Shares available for future equity grants under the 2005 Equity Plan		1,874,202	1,400,000
Shares available for future equity grants under the 1997 ESPP Plan								568,915
Shares issued under the Plan	68,439
Stock options outstanding to employees		400,646		432,314	128,916
Stock options outstanding		3,216,696
Stock options outstanding, Exercisable		2,219,521
Weighted-average exercise price of stock options		$ 12.59
Aggregate intrinsic value of stock options		$ 2.6		$ 6.8
Weighted average remaining contractual term stock options		5.6
Restricted stock units outstanding				674,129
Restricted stock units weighted average remaining vesting period				3.0
Weighted-average exercise price of stock options, Exercisable		$ 13.41
Aggregate intrinsic value of stock options, Exercisable		$ 1.8
Weighted average remaining contractual term stock options, Exercisable		4.3
Number of common share granted		400,646		432,314	128,916
Award measurement period					1 year
Period in which restricted stock unit vest					3 years
Common stock granted on achievement of performance goals						150.00%	0.00%