Consolidated Statements of Shareholders' Equity (USD $) In Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Treasury Stock [Member]
Balance at Dec. 31, 2010	$ 106,972	$ 481	$ 153,576	$ (275)	$ 102,558	$ (149,368)
Balance, shares at Dec. 31, 2010		48,148				(15,854)
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	3,553		(10,352)			13,905
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	2,045		(230)			2,275
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
Issuance of shares for acquisition
Issuance of shares for acquisition, shares
Balance at Dec. 31, 2011	78,110	481	152,859	(355)	130,115	(204,990)
Balance, shares at Dec. 31, 2011		48,148				(18,176)
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	12,443		(17,018)			29,461
Issuance of shares pursuant to stock compensation plan, shares	1,218					1,218
Stock compensation	7,411		7,411
Treasury stock purchases
Treasury stock purchases, shares
Issuance of shares pursuant to Employee Stock Purchase Plan	2,641		639			2,002
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	2,815		1,329			1,486
Issuance of shares for acquisition, shares	60					60
Balance at Dec. 31, 2012	145,299	481	154,018	(268)	163,109	(172,041)
Balance, shares at Dec. 31, 2012		48,148				(16,817)
Net income	39,101				39,101
Unrealized gain (loss) on investment securities, net of tax	222			222
Issuance of shares pursuant to stock compensation plan	18,289		(13,742)			32,031
Issuance of shares pursuant to stock compensation plan, shares	1,443					1,443
Stock compensation	11,653		11,653
Treasury stock purchases
Treasury stock purchases, shares
Issuance of shares pursuant to Employee Stock Purchase Plan	3,542		2,034			1,508
Issuance of shares pursuant to Employee Stock Purchase Plan, shares	64					64
Federal income tax benefit related to exercise of stock options	28,213		28,213
Issuance of shares for acquisition
Issuance of shares for acquisition, shares
Balance at Dec. 31, 2013	$ 246,319	$ 481	$ 182,176	$ (46)	$ 202,210	$ (15,310)
Balance, shares at Dec. 31, 2013		48,148				(15,310)