Consolidated Statements Of Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Total		Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income, net of taxes [Member]	Retained Earnings [Member]	Treasury Stock [Member]
Balance at Dec. 31, 2012	$ 229,570		$ 700	$ 113,495	$ 127	$ 127,042	$ (11,794)
Balance, Shares at Dec. 31, 2012			70,036
Comprehensive income:
Net income for the period	14,954					14,954
Unrealized gain on available for sale marketable securities, net of taxes	23	[1]			23
Comprehensive Income	14,977
Exercise of stock options and other stock-based compensation, net of shares tendered for payment	3,640		3	3,596			41
Exercise of stock options and other stock-based compensation, net of shares tendered for payment, Shares			273
Tax benefit from equity compensation plans	709			709
Share-based compensation expense - stock options and restricted stock	494			494
Treasury shares issued for Deferred Compensation Plan funding and redemptions	364			358			6
Shares issued pursuant to Employee Stock Plans	1,842			1,371			471
Cash dividends	(11,415)					(11,415)
Shares issued pursuant to Dividend Reinvestment Plan	27			81			(54)
Balance at Mar. 31, 2013	$ 240,208		$ 703	$ 120,104	$ 150	$ 130,581	$ (11,330)
Balance, Shares at Mar. 31, 2013			70,309

[1] All amounts are net of tax.