Consolidated Statements Of Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Total		Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income [Member]	Retained Earnings [Member]	Treasury Stock [Member]
Balance at Dec. 31, 2010	$ 213,079		$ 693	$ 100,138	$ (78)	$ 130,993	$ (18,667)
Balance (in shares) at Dec. 31, 2010			69,315
Comprehensive income:
Net income	38,156					38,156
Unrealized gain/(loss) on available for sale marketable securities, net of taxes	421				421
Total comprehensive income	38,577
Exercise of stock options and other stock-based compensation, net of shares tendered for payment	2,363		2	349			2,012
Exercise of stock options and other stock-based compensation, net of shares tendered for payment (in shares)			158
Tax benefit from equity compensation plans	1,222			1,222
Share-based compensation expense — stock options and restricted stock	1,870			1,870
Treasury shares issued for Deferred Compensation Plan funding and redemptions	402			367			35
Shares issued pursuant to Employee Stock Plans	1,233			782			451
Cash dividends	(42,228)					(42,228)
Shares issued pursuant to Dividend Reinvestment Plan	128			81			47
Shares issued pursuant to acquisition	1,080			918			162
Balance at Dec. 31, 2011	217,726		695	105,727	343	126,921	(15,960)
Balance (in shares) at Dec. 31, 2011			69,473
Comprehensive income:
Net income	44,214					44,214
Unrealized gain/(loss) on available for sale marketable securities, net of taxes	(216)				(216)
Total comprehensive income	43,998
Exercise of stock options and other stock-based compensation, net of shares tendered for payment	5,573		5	4,098			1,470
Exercise of stock options and other stock-based compensation, net of shares tendered for payment (in shares)			563
Tax benefit from equity compensation plans	2,649			2,649
Share-based compensation expense — stock options and restricted stock	1,897			1,897
Treasury shares issued for Deferred Compensation Plan funding and redemptions	453			394			59
Shares issued pursuant to Employee Stock Plans	1,249			1,278			(29)
Cash dividends	(44,093)					(44,093)
Shares issued pursuant to Dividend Reinvestment Plan	118			85			33
Shares issued pursuant to acquisition	0			(2,633)			2,633
Balance at Dec. 31, 2012	229,570		700	113,495	127	127,042	(11,794)
Balance (in shares) at Dec. 31, 2012			70,036
Comprehensive income:
Net income	47,129					47,129
Unrealized gain/(loss) on available for sale marketable securities, net of taxes	(78)	[1]			(78)
Total comprehensive income	47,051
Exercise of stock options and other stock-based compensation, net of shares tendered for payment	6,428		7	6,381			40
Exercise of stock options and other stock-based compensation, net of shares tendered for payment (in shares)			617
Tax benefit from equity compensation plans	2,615			2,615
Share-based compensation expense — stock options and restricted stock	2,045			2,045
Treasury shares issued for Deferred Compensation Plan funding and redemptions	360			294			66
Shares issued pursuant to Employee Stock Plans	1,842			1,370			472
Cash dividends	(46,707)					(46,707)
Shares issued pursuant to Dividend Reinvestment Plan	107			309			(202)
Shares issued pursuant to acquisition	41,832		12	41,820			0
Shares issued pursuant to acquisition (in shares)			1,215
Balance at Dec. 31, 2013	$ 285,143		$ 719	$ 168,329	$ 49	$ 127,464	$ (11,418)
Balance (in shares) at Dec. 31, 2013			71,868

[1] All amounts are net of tax.