Consolidated Statements Of Stockholders' Equity (Unaudited) - 9 months ended Sep. 30, 2015 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income, net of taxes	Retained Earnings	Treasury Stock
Balance (in shares) at Dec. 31, 2014		72,878
Balance at Dec. 31, 2014	$ 275,830	$ 729	$ 186,022	$ 25	$ 100,237	$ (11,183)
Comprehensive income:
Net income for the period	48,890				48,890
Unrealized gain on available for sale marketable securities, net of taxes	181			181
Total comprehensive income (loss)	49,071
Exercise of stock options, net of shares tendered for payment (in shares)		285
Exercise of stock options, net of shares tendered for payment	4,937	$ 3	4,934
Tax benefit from equity compensation plans	1,062		1,062
Share-based compensation expense — stock options and restricted stock	2,280		2,280
Treasury shares issued for Deferred Compensation Plan funding and redemptions	492		422			70
Shares issued pursuant to Employee Stock Purchase Plan	1,701		1,363			338
Cash dividends	(38,338)				(38,338)
Shares issued pursuant to Dividend Reinvestment Plan	83		255			(172)
Shares issued pursuant to prior year acquisition (in shares)		529
Shares issued pursuant to prior year acquisition	0	$ 5	(5)
Balance (in shares) at Sep. 30, 2015		73,692
Balance at Sep. 30, 2015	$ 297,118	$ 737	$ 196,333	$ 206	$ 110,789	$ (10,947)