Stock Based Compensation - Options Rollforward (Details) (USD $)	9 Months Ended
	Sep. 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	(167,025)
Options Forfeited	(8,470)
Ending Balance	118,004
Options Exerciseable	27,909
Weighted Average Exercise Price [Abstract]
Outstanding at beginning of year	$ 16.43
Options Granted	$ 38.57
Options Exercised	$ 12.00
Options Forfeited	$ 29.32
Outstanding at End of Period	$ 29.31
Options Exercisable	$ 21.63
Weighted Average Contractual Term [Abstract]
Weighted Average Remaining Contractual Term, Outstanding	5 years 2 months
Weighted Average Remaining Contractual Term, Exercisable	4 years 4 months