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, 2014		31,862,294	7,197,532
Compensation expense related to granting of restricted stock awards SHARES		738,195	0
Exercise of stock options SHARES		11,750	0
Purchase of vested employee restricted stock units SHARES		(131,688)	0
Ending Balance SHARES at Dec. 31, 2015		32,480,551	7,197,532
Opening Balance VALUE at Dec. 31, 2014	$ 329,021	$ 319	$ 72	$ 608,515	$ (279,885)
Net income (loss)	29,184				29,184
Compensation expense related to granting of restricted stock awards VALUE	5,524	7	0	5,517	0
Purchase of vested employee restricted stock units	(1,562)	(1)	0	(1,561)	0
Forfeitures of dividend equivalents VALUE	0	0	0	0	0
Realization of tax benefit for dividend equivalent payments VALUE	35	0	0	35	0
Preferred stock dividend	(752)			(752)
Ending Balance VALUE at Dec. 31, 2015	$ 361,450	$ 325	$ 72	611,754	(250,701)
Compensation expense related to granting of stock options SHARES	0
Compensation expense related to granting of restricted stock awards SHARES		1,092,510	0
Issuance of common stock related to an incentive plan SHARES		17,665	0
Exercise of stock options SHARES	29,500	29,500	0
Purchase of vested employee restricted stock units SHARES		(228,008)	0
Ending Balance SHARES at Sep. 30, 2016		33,392,218	7,197,532
Net income (loss)	$ 26,666				26,666
Compensation expense related to granting of restricted stock awards VALUE	4,660	$ 11	$ 0	4,649	0
Issuance of common stock related to an incentive plan VALUE	194	0	0	194
Purchase of vested employee restricted stock units	(2,205)	(2)	0	(2,203)	0
Payments of dividends VALUE	(5,772)	0	0	(5,772)	0
Forfeitures of dividend equivalents VALUE	(447)	0	0	(447)	0
Exercise of stock options VALUE	39	0	0	39	0
Preferred stock dividend	(1,238)	0	0	(1,238)	0
Ending Balance VALUE at Sep. 30, 2016	$ 383,347	$ 334	$ 72	$ 606,976	$ (224,035)