CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $) In Thousands, except Share data	Total	Common Class A [Member]	Common Class B [Member]	Additional Paid In Capital [Member]	Retained Earnings [Member]
Opening Balance VALUE at Dec. 31, 2011	$ 253,688	$ 310	$ 72	$ 597,327	$ (344,021)
Opening Balance SHARES at Dec. 31, 2011		31,044,001	7,197,532
Conversion of Class B common stock to Class A common stock SHARES		0	0
Compensation expense related to granting of restricted stock awards SHARES		280,072	0
Issuance of common stock related to an incentive plan SHARES		0	0
Common stock repurchase SHARES		0	0
Exercise of stock options SHARES		101,350	0
Purchase of vested employee restricted stock units SHARES	(199,000)	(199,376)	0
Net income (loss)	11,268				11,268
Compensation expense related to granting of restricted stock awards VALUE	5,754	3	0	5,751	0
Issuance of common stock related to an incentive plan VALUE	0	0	0	0	0
Common stock repurchase VALUE	0	0	0	0	0
Purchase of vested employee restricted stock units	(1,367)	(2)	0	(1,365)	0
Forfeitures of dividend equivalents VALUE	16	0	0	0	16
Realization of tax benefit for dividend equivalent payments VALUE	0	0	0	0	0
Exercise of stock options VALUE	135	1	0	134	0
Net unrealized gain (loss) on investments VALUE		0
Net unrealized gain (loss) on derivatives VALUE	0		0	0	0
Ending Balance VALUE at Dec. 31, 2012	269,494	312	72	601,847	(332,737)
Ending Balance SHARES at Dec. 31, 2012		31,226,047	7,197,532
Conversion of Class B common stock to Class A common stock SHARES		0	0
Compensation expense related to granting of restricted stock awards SHARES		96,560	0
Issuance of common stock related to an incentive plan SHARES		0	0
Common stock repurchase SHARES		0	0
Exercise of stock options SHARES		171,625	0
Purchase of vested employee restricted stock units SHARES	(186,000)	(186,038)	0
Net income (loss)	26,024				26,024
Compensation expense related to granting of restricted stock awards VALUE	4,270	1	0	4,269	0
Issuance of common stock related to an incentive plan VALUE	0	0	0	0	0
Common stock repurchase VALUE	0	0	0	0	0
Purchase of vested employee restricted stock units	(1,640)	(2)	0	(1,638)	0
Forfeitures of dividend equivalents VALUE	0	0	0	0	0
Realization of tax benefit for dividend equivalent payments VALUE	0	0	0	0	0
Exercise of stock options VALUE	245	2	0	243	0
Net unrealized gain (loss) on derivatives VALUE		0	0	0	0
Ending Balance VALUE at Dec. 31, 2013	298,393	313	72	604,721	(306,713)
Ending Balance SHARES at Dec. 31, 2013		31,308,194	7,197,532
Conversion of Class B common stock to Class A common stock SHARES		0	0
Compensation expense related to granting of stock options SHARES	0
Compensation expense related to granting of restricted stock awards SHARES		638,102	0
Issuance of common stock related to an incentive plan SHARES		0	0
Exercise of stock options SHARES	57,500	57,500	0
Purchase of vested employee restricted stock units SHARES	(142,000)	(141,502)	0
Net income (loss)	26,823				26,823
Compensation expense related to granting of restricted stock awards VALUE	5,232	7	0	5,225	0
Issuance of common stock related to an incentive plan VALUE	0	0	0	0	0
Common stock repurchase VALUE	0	0	0	0	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
Exercise of stock options VALUE	82	0	0	82	0
Net unrealized gain (loss) on investments VALUE	0	0	0	0	0
Net unrealized gain (loss) on derivatives VALUE	0	0	0	0	0
Ending Balance VALUE at Dec. 31, 2014	$ 329,021	$ 319	$ 72	$ 608,515	$ (279,885)
Ending Balance SHARES at Dec. 31, 2014		31,862,294	7,197,532