CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS EQUITY (USD $) In Thousands	Total	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]
Beginning balance at Dec. 31, 2011	$ 714,814	$ 479,973	$ 193,372	$ 41,469
Beginning balance, shares at Dec. 31, 2011		104,482
Exercise of stock options	1,355	1,355
Exercise of stock options, shares		225
Tax benefit from exercise of stock options	110	110
Shares issued pursuant to stock-based compensation plan	405	405
Cash dividends declared Common ($0.085 per share)	(8,903)		(8,903)
Net earnings	22,268		22,268
Other comprehensive income	(42)			(42)
Ending balance at Mar. 31, 2012	730,007	481,843	206,737	41,427
Ending balance, shares at Mar. 31, 2012		104,707
Beginning balance at Dec. 31, 2012	762,970	484,709	235,010	43,251
Beginning balance, shares at Dec. 31, 2012		104,890
Repurchase of common stock	(24)	(24)
Repurchase of common stock, Shares		(2)
Exercise of stock options	95	95
Exercise of stock options, shares		10
Tax benefit from exercise of stock options	5	5
Shares issued pursuant to stock-based compensation plan	461	461
Shares issued pursuant to stock-based compensation plan, shares		5
Cash dividends declared Common ($0.085 per share)	(8,912)		(8,912)
Net earnings	21,615		21,615
Other comprehensive income	(7,998)			(7,998)
Ending balance at Mar. 31, 2013	$ 768,212	$ 485,246	$ 247,713	$ 35,253
Ending balance, shares at Mar. 31, 2013		104,903