Stock Based Compensation (Details 3) (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Common stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares	29
Weighted-average grant date fair value, awarded	$ 31.49
Aggregate fair value	$ 920
Restricted stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares	313
Weighted-average grant date fair value, awarded	$ 31.20
Aggregate fair value	9,758
Restricted stock [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	2 years
Restricted stock [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Restricted stock units (RSU) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares	13
Weighted-average grant date fair value, awarded	$ 30.60
Aggregate fair value	403
Restricted stock units (RSU) [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Restricted stock units (RSU) [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares	218
Weighted-average grant date fair value, awarded	$ 8.00
Aggregate fair value	$ 1,741
Stock Options [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year
Stock Options [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	5 years