CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (unaudited) (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		(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
Net dividend equivalents on restricted stock units net of forfeitures and payments 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 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		0	0
Compensation expense related to granting of stock options SHARES		0	0
Compensation expense related to granting of restricted stock units SHARES		426,501	0
Issuance of common stock related to an incentive plan SHARES		0	0
Common stock repurchase SHARES		0	0
Exercise of stock options SHARES		49,875	0
Purchase of vested employee restricted stock units SHARES		(282,973)	0
Net income (loss)	49,755	0	0	0	49,755	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	249	0	0	249	0	0
Compensation expense related to granting of restricted stock units VALUE	4,417	5	0	4,412	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	(2,976)	(3)	0	(2,973)	0	0
Payments of dividends VALUE	0	0	0	0	0	0
Net dividend equivalents on restricted stock units net of forfeitures and payments VALUE	3	0	0	0	3	0
Exercise of stock options VALUE	66	0	0	66	0	0
Net unrealized gain (loss) on investments VALUE	0	0	0	0	0	0
Net unrealized gain (loss) on derivatives VALUE	8,135	0	0	0	0	8,135
Ending Balance VALUE at Jun. 30, 2011	$ 230,316	$ 309	$ 74	$ 594,397	$ (365,322)	$ 858
Ending Balance SHARES at Jun. 30, 2011		30,893,971	7,367,532