Statements Of Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Total
Balance at Dec. 31, 2009	$ 481	$ 153,734	$ (405)	$ 77,504	$ (96,956)	$ 134,358
Balance, shares at Dec. 31, 2009	48,148				(13,028)
Comprehensive income:
Net income				25,054		25,054
Unrealized gain (loss) on investment securities, net of tax			130			130
Issuance of shares pursuant to stock compensation plan		(8,157)			11,338	3,181
Issuance of shares pursuant to stock compensation plan, shares					615	615
Stock compensation		6,132				6,132
Treasury stock purchases					(65,793)	(65,793)
Treasury stock purchases, shares					(3,559)	(3,559)
Issuance of shares pursuant to Employee Stock Purchase Plan		(218)			2,043	1,825
Issuance of shares pursuant to Employee Stock Purchase Plan, shares					118	118
Federal income tax benefit related to exercise of stock options		2,085				2,085
Balance at Dec. 31, 2010	481	153,576	(275)	102,558	(149,368)	106,972
Balance, shares at Dec. 31, 2010	48,148				(15,854)
Comprehensive income:
Net income				27,557		27,557
Unrealized gain (loss) on investment securities, net of tax			(80)			(80)
Issuance of shares pursuant to stock compensation plan		(10,352)			13,905	3,553
Issuance of shares pursuant to stock compensation plan, shares					582	582
Stock compensation		6,253				6,253
Treasury stock purchases					(71,802)	(71,802)
Treasury stock purchases, shares					(3,004)	(3,004)
Issuance of shares pursuant to Employee Stock Purchase Plan		(230)			2,275	2,045
Issuance of shares pursuant to Employee Stock Purchase Plan, shares					100	100
Federal income tax benefit related to exercise of stock options		3,612				3,612
Balance at Dec. 31, 2011	481	152,859	(355)	130,115	(204,990)	78,110
Balance, shares at Dec. 31, 2011	48,148				(18,176)
Comprehensive income:
Net income				32,994		32,994
Unrealized gain (loss) on investment securities, net of tax			87			87
Issuance of shares pursuant to stock compensation plan		(17,018)			29,461	12,443
Issuance of shares pursuant to stock compensation plan, shares					1,218	1,218
Stock compensation		7,411				7,411
Issuance of shares pursuant to Employee Stock Purchase Plan		639			2,002	2,641
Issuance of shares pursuant to Employee Stock Purchase Plan, shares					81	81
Federal income tax benefit related to exercise of stock options		8,798				8,798
Issuance of shares for acquisition		1,329			1,486	2,815
Issuance of shares for acquisition, shares					60	60
Balance at Dec. 31, 2012	$ 481	$ 154,018	$ (268)	$ 163,109	$ (172,041)	$ 145,299
Balance, shares at Dec. 31, 2012	48,148				(16,817)