Consolidated Statements Of Shareholders' Equity (USD $) In Thousands	Common Stock [Member]	Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance at Dec. 31, 2008	$ 306	$ 11,829	$ 328,178	$ (2,562)	$ 337,751
Balance, shares at Dec. 31, 2008	30,607
Net income	0	0	146,255	0	146,255
Other comprehensive income	0	0	0	1,658	1,658
Stock-based compensation	0	6,805	0	0	6,805
Restricted stock awards, net of forfeitures	0	0	0	0	0
Restricted stock awards, net of forfeitures, shares	103
Repurchase of common stock	0	(541)	0	0	(541)
Repurchase of common stock, shares	(31)
Stock options exercised	5	1,936	0	0	1,941
Stock options exercised, shares	359
Tax benefits from stock-based compensation plans	0	4,341	0	0	4,341
Balance at Dec. 31, 2009	311	24,370	474,433	(904)	498,210
Balance, shares at Dec. 31, 2009	31,038
Net income	0	0	170,077	0	170,077
Other comprehensive income	0	0	0	794	794
Stock-based compensation	0	4,127	0	0	4,127
Restricted stock awards, net of forfeitures	0	0	0	0	0
Restricted stock awards, net of forfeitures, shares	13
Repurchase of common stock	(41)	(1,022)	(201,184)	0	(202,247)
Repurchase of common stock, shares	(4,047)
Stock options exercised	3	2,900	0	0	2,903
Stock options exercised, shares	300
Tax benefits from stock-based compensation plans	0	610	0	0	610
Balance at Dec. 31, 2010	273	30,985	443,326	(110)	474,474
Balance, shares at Dec. 31, 2010	27,304				27,304
Net income	0	0	188,044	0	188,044
Other comprehensive income	0	0	0	116	116
Stock-based compensation	0	1,881	0	0	1,881
Restricted stock awards, net of forfeitures	0	0	0	0	0
Restricted stock awards, net of forfeitures, shares	(1)
Repurchase of common stock	(20)	(384)	(130,482)	0	(130,886)
Repurchase of common stock, shares	(1,979)
Stock options exercised	3	2,918	0	0	2,921
Stock options exercised, shares	300
Tax benefits from stock-based compensation plans	0	3,401	0	0	3,401
Balance at Dec. 31, 2011	$ 256	$ 38,801	$ 500,888	$ 6	$ 539,951
Balance, shares at Dec. 31, 2011	25,624				25,624