Income Per Share - (Narrative) (Details) - $ / shares	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Shares outstanding	26,282,224	26,802,964	26,282,224
Outstanding stock options to purchase common stock	2,669,859	1,661,140	2,669,859	2,185,922
Outstanding stock options to purchase common stock, per share	$ 19.82	$ 20.62	$ 19.82	$ 19.81
Warrants granted, exercise price per share	$ 20.00	$ 20.00	$ 20.00	$ 20.00
Restricted shares outstanding		372,252	912,783
Warrant [Member]
Dilutive Convertible Securities	70,182	11,243	27,343