CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands	Total	Class A Common Stock	Class B Convertible Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Beginning Balance at Dec. 31, 2011	$ 168,978	$ 15	$ 2	$ 457,837	$ (475,184)	$ (2,052)	$ 188,360
Beginning Balance (in shares) at Dec. 31, 2011		14,810	2,378		(6,405)
Net income (loss)	20,546	0	0	0	0	0	20,546
Other comprehensive (loss) income	537	0	0	0	0	537	0
Conversion of class B to class A common stock	0	0	0	0	0	0	0
Conversion of class B to class A common stock (in shares)		151	(151)		0
Issuance of class A common stock under stock option plans	10,250	0	0	10,250	0	0	0
Issuance of class A common stock under stock option plans (in shares)	501	501	0		0
Ending Balance at Dec. 31, 2012	200,311	15	2	468,087	(475,184)	(1,515)	208,906
Ending Balance (in shares) at Dec. 31, 2012		15,462	2,227		(6,405)
Net income (loss)	83,332	0	0	0	0	0	83,332
Other comprehensive (loss) income	684	0	0	0	0	684	0
Issuance of class A common stock under stock option plans	341	0	0	341	0	0	0
Issuance of class A common stock under stock option plans (in shares)	16	16	0		0
Tax effect of stock option exercises	23,580	0	0	23,580	0	0	0
Share-based compensation expense	2,078	0	0	2,078	0	0	0
Ending Balance at Dec. 31, 2013	310,326	15	2	494,086	(475,184)	(831)	292,238
Ending Balance (in shares) at Dec. 31, 2013		15,478	2,227		(6,405)
Net income (loss)	5,035	0	0	0	0	0	5,035
Other comprehensive (loss) income	(3,532)	0	0	0	0	(3,532)	0
Conversion of class B to class A common stock	0	0	0	0	0	0	0
Conversion of class B to class A common stock (in shares)		172	(172)		0
Issuance of class A common stock under stock option plans	856	1	0	855	0	0	0
Issuance of class A common stock under stock option plans (in shares)	9	10	0		0
Share-based compensation expense	11,786	0	0	11,786	0	0	0
Ending Balance at Dec. 31, 2014	$ 324,471	$ 16	$ 2	$ 506,727	$ (475,184)	$ (4,363)	$ 297,273
Ending Balance (in shares) at Dec. 31, 2014		15,660	2,055		(6,405)