Stock Based Compensation - Options Rollforward (Details) (USD $)	6 Months Ended
	Jun. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning Balance	253,342
Options Granted	40,157
Options Exercised	(77,176)
Options Forfeited	(8,470)
Ending Balance	207,853
Options Exerciseable	117,758
Weighted Average Exercise Price [Abstract]
Outstanding at beginning of year	$ 16.43
Options Granted	$ 38.57
Options Exercised	$ 9.62
Options Forfeited	$ 29.32
Outstanding at End of Period	$ 22.72
Options Exercisable	$ 15.85
Weighted Average Contractual Term [Abstract]
Weighted Average Remaining Contractual Term, Outstanding	4 years 6 months
Weighted Average Remaining Contractual Term, Exercisable	3 years 6 months