Stock Based Compensation (Details 1) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Intrinsic value and net shares issued for restricted stock units
Intrinsic value, Total	$ 1,869	$ 1,729	$ 6,878	$ 6,998
Net shares issued	299	595	1,100	2,469
RSUs vested [Member]
Intrinsic value and net shares issued for restricted stock units
Intrinsic value, Total	356	857	3,258	4,598
Net shares issued	18	67	191	362
MSUs vested [Member]
Intrinsic value and net shares issued for restricted stock units
Intrinsic value, Total			511
Net shares issued			30
Options exercised [Member]
Intrinsic value and net shares issued for restricted stock units
Intrinsic value, Total	1,335	814	2,832	2,300
Net shares issued	243	504	817	2,053
Shares purchased pursuant to ESPP [Member]
Intrinsic value and net shares issued for restricted stock units
Intrinsic value, Total	$ 178	$ 58	$ 277	$ 100
Net shares issued	38	24	62	54