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]	Accumulated Other Comprehensive Income (Loss) [Member]
Opening Balance VALUE at Dec. 31, 2009	$ 113,952	$ 297	$ 75	$ 588,622	$ (461,610)	$ (13,432)
Opening Balance SHARES at Dec. 31, 2009		29,755,161	7,457,532
Conversion of Class B common stock to Class A common stock SHARES		90,000	(90,000)
Compensation expense related to granting of stock options SHARES		0	0
Compensation expense related to granting of restricted stock units SHARES		941,213	0
Issuance of common stock related to an incentive plan SHARES		0	0
Common stock repurchase SHARES		0	0
Exercise of stock options SHARES		97,725	0
Purchase of vested employee restricted stock units SHARES	(182,000)	(183,531)	0
Net income (loss)	46,436	0	0	0	46,436	0
Conversion of Class B common stock to Class A common stock VALUE	0	1	(1)	0	0	0
Compensation expense related to granting of stock options VALUE	549	0	0	549	0	0
Compensation expense related to granting of restricted stock units VALUE	4,979	10	0	4,969	0	0
Issuance of common stock related to an incentive plan VALUE	0	0	0	0	0	0
Common stock repurchase VALUE	0	0	0	0	0	0
Purchase of vested employee restricted stock units	(1,628)	(2)	0	(1,626)	0	0
Forfeitures of dividend equivalents VALUE	94	0	0	0	94	0
Realization of tax benefit for dividend equivalent payments VALUE	0	0	0	0	0	0
Exercise of stock options VALUE	130	1	0	129	0	0
Net unrealized gain (loss) on investments VALUE	0	0	0	0	0	0
Net unrealized gain (loss) on derivatives VALUE	6,155	0	0	0	0	6,155
Ending Balance VALUE at Dec. 31, 2010	170,667	307	74	592,643	(415,080)	(7,277)
Ending Balance SHARES at Dec. 31, 2010		30,700,568	7,367,532
Conversion of Class B common stock to Class A common stock SHARES		170,000	(170,000)
Compensation expense related to granting of stock options SHARES		0	0
Compensation expense related to granting of restricted stock units SHARES		416,906	0
Issuance of common stock related to an incentive plan SHARES		0	0
Common stock repurchase SHARES		0	0
Exercise of stock options SHARES		53,625	0
Purchase of vested employee restricted stock units SHARES	(297,000)	(297,098)	0
Net income (loss)	66,277	0	0	0	66,277	0
Conversion of Class B common stock to Class A common stock VALUE	0	2	(2)	0	0	0
Compensation expense related to granting of stock options VALUE	462	0	0	462	0	0
Compensation expense related to granting of restricted stock units VALUE	7,209	4	0	7,205	0	0
Issuance of common stock related to an incentive plan VALUE	0	0	0	0	0	0
Common stock repurchase VALUE	0	0	0	0	0	0
Purchase of vested employee restricted stock units	(3,057)	(3)	0	(3,054)	0	0
Forfeitures of dividend equivalents VALUE	5	0	0	0	5	0
Realization of tax benefit for dividend equivalent payments VALUE	0	0	0	0	0	0
Exercise of stock options VALUE	71	0	0	71	0	0
Net unrealized gain (loss) on derivatives VALUE	7,277	0	0	0	0	7,277
Ending Balance VALUE at Dec. 31, 2011	248,911	310	72	597,327	(348,798)	0
Ending 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 stock options SHARES	0	0	0
Compensation expense related to granting of restricted stock units 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)	101,350	0
Purchase of vested employee restricted stock units SHARES	(199,000)	(199,376)	0
Net income (loss)	11,268	0	0	0	11,268	0
Conversion of Class B common stock to Class A common stock VALUE	0	0	0	0	0	0
Compensation expense related to granting of stock options VALUE	210	0	0	210	0	0
Compensation expense related to granting of restricted stock units VALUE	5,544	3	0	5,541	0	0
Issuance of common stock related to an incentive plan VALUE	0	0	0	0	0	0
Common stock repurchase VALUE	0	0	0	0	0	0
Purchase of vested employee restricted stock units	(1,367)	(2)	0	(1,365)	0	0
Payments of dividends VALUE	0	0	0	0	0	0
Forfeitures of dividend equivalents VALUE	16	0	0	0	16	0
Exercise of stock options VALUE	135	1	0	134	0	0
Net unrealized gain (loss) on investments VALUE	0	0	0	0	0	0
Net unrealized gain (loss) on derivatives VALUE	0	0	0	0	0	0
Ending Balance VALUE at Dec. 31, 2012	$ 264,717	$ 312	$ 72	$ 601,847	$ (337,514)	$ 0
Ending Balance SHARES at Dec. 31, 2012		31,226,047	7,197,532