Stock-Based Compensation - Share Option Activity (Details) (Stock Options [Member], USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding (in shares)	312,000
Grants in period (in shares)	0
Exercised (in shares)	(50,225)
Forfeited or expired (in shares)	(5,875)
Outstanding (in shares)	255,900		312,000
Exercisable (in shares)	74,900
Vested or expected to vest (in shares)	245,167.84
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding, weighted-average exercise price (in dollars per share)	$ 9.33
Granted, weighted-average exercise price (in dollers per share)	$ 0.00
Exercised, weighted-average exercise price (in dollars per share)	$ 8.22
Forfeited or expired, weighted-average exercise price (in dollars per share)	$ 9.44
Outstanding, weighted-average exercise price (in dollars per share)	$ 9.55		$ 9.33
Exercisable, weighted-average exercise price (in dollars per share)	$ 9.14
Vested or expected to vest, weighted-average exercise price (in dollars per share)	$ 9.52
Outstanding, average remaining contractual term (in years)	8 years 2 months 12 days		8 years 10 months 24 days
Exercisable, average remaining contractual term (in years)	8 years
Vested or expected to vest, average remaining contractual term	8 years 2 months 12 days
Outstanding, aggregate intrinsic value	$ 1,927,000		$ 1,946,000
Exercisable, aggregate intrinsic value	595,000
Vested or expected to vest, aggregate intrinsic value	1,854,000
Total instrinsic value of share options exercised	600,000
Total fair value of options vested during the period	$ 300,000	$ 300,000