CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Class A [Member]	Common Class B [Member]	Additional Paid In Capital [Member]	Retained Earnings [Member]
Opening Balance SHARES at Dec. 31, 2013		31,308,194	7,197,532
Compensation expense related to granting of restricted stock awards SHARES		638,102	0
Exercise of stock options SHARES		57,500	0
Purchase of vested employee restricted stock units SHARES		(141,502)	0
Ending Balance SHARES at Dec. 31, 2014		31,862,294	7,197,532
Opening Balance VALUE at Dec. 31, 2013	$ 298,393	$ 313	$ 72	$ 604,721	$ (306,713)
Net income (loss)	26,823				26,823
Compensation expense related to granting of restricted stock awards VALUE	5,232	7	0	5,225	0
Purchase of vested employee restricted stock units	(1,514)	(1)	0	(1,513)	0
Forfeitures of dividend equivalents VALUE	5	0	0	0	5
Realization of tax benefit for dividend equivalent payments VALUE	82	0	0	82	0
Ending Balance VALUE at Dec. 31, 2014	$ 329,021	$ 319	$ 72	608,515	(279,885)
Compensation expense related to granting of stock options SHARES	0
Compensation expense related to granting of restricted stock awards SHARES		648,029	0
Common stock repurchase SHARES		11,750	0
Exercise of stock options SHARES	11,750
Purchase of vested employee restricted stock units SHARES		(128,523)	0
Ending Balance SHARES at Sep. 30, 2015		32,393,550	7,197,532
Net income (loss)	$ 15,096				15,096
Compensation expense related to granting of restricted stock awards VALUE	4,097	$ 6	$ 0	4,091	0
Purchase of vested employee restricted stock units	(1,527)	(1)	0	(1,526)	0
Realization of tax benefit for dividend equivalent payments VALUE	35	0	0	35	0
Preferred stock dividend	(339)	0	0	(339)	0
Ending Balance VALUE at Sep. 30, 2015	$ 346,383	$ 324	$ 72	$ 610,776	$ (264,789)