Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock Shares [Member]	Non-Redeemable Preferred Stock [Member]	Capital in Excess of Par Value [Member]	Retained Earnings [Member]	Treasury Stock-Common [Member]
Balance at Dec. 31, 2009	$ 150,607	$ 2,537	$ 3,000	$ 129,941	$ 41,082	$ (25,953)
Balance, shares at Dec. 31, 2009		25,369,000
Net income	29,574				29,574
Dividends paid on preferred stocks	(305)				(305)
Stock-based compensation	1,005			1,005
Exercise of stock options	829	11		818
Exercise of stock options, shares		106,000
Excess income tax benefit associated with stock-based compensation	78			78
Acquisition of 177,100 shares of common stock	(2,421)					(2,421)
Conversion of 37,13 and 68 shares of redeemable preferred stock to common stock in 2010, 2011 and 2012 respectively	3			3
Conversion of redeemable preferred stock to common stock, shares		2,000
Balance at Dec. 31, 2010	179,370	2,548	3,000	131,845	70,351	(28,374)
Balance, shares at Dec. 31, 2010		25,477,000
Net income	83,842				83,842
Dividends paid on preferred stocks	(305)				(305)
Stock-based compensation	1,099			1,099
Conversion of convertible debt to common stock	26,904	98		26,806
Conversion of convertible debt to common stock, shares		983,000
Exercise of stock options	1,197	18		1,179
Exercise of stock options, shares		178,000
Excess income tax benefit associated with stock-based compensation	1,162			1,162
Conversion of 37,13 and 68 shares of redeemable preferred stock to common stock in 2010, 2011 and 2012 respectively	1			1
Conversion of redeemable preferred stock to common stock, shares	979,160
Balance at Dec. 31, 2011	293,270	2,664	3,000	162,092	153,888	(28,374)
Balance, shares at Dec. 31, 2011		26,638,000
Net income	58,604				58,604
Dividends paid on preferred stocks	(300)				(300)
Stock-based compensation	1,652			1,652
Exercise of stock options	767	9		758
Exercise of stock options, shares		90,000
Excess income tax benefit associated with stock-based compensation	498			498
Conversion of 37,13 and 68 shares of redeemable preferred stock to common stock in 2010, 2011 and 2012 respectively	6			6
Conversion of redeemable preferred stock to common stock, shares		3,000
Balance at Dec. 31, 2012	$ 354,497	$ 2,673	$ 3,000	$ 165,006	$ 212,192	$ (28,374)
Balance, shares at Dec. 31, 2012		26,731,000