CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Common Stock [Member]	Capital In Excess of Par [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance at Dec. 31, 2009	$ 31,618	$ 55,617	$ 421,908	$ (35,539)	$ (37,926)	$ 435,678
Balance (in shares) at Dec. 31, 2009	29,770,840
Comprehensive income:
Net earnings			43,823			43,823
Other comprehensive income, net of tax					1,280	1,280
Cash dividends			(15,017)			(15,017)
Treasury stock purchases				0		0
Treasury stock purchases (in shares)	0
Tax settlement on stock-based compensation		0				0
Stock-based compensation		4,627				4,627
Exercise of stock options	515	14,567		487		15,569
Exercise of stock options (in shares)	533,641
Balance at Dec. 31, 2010	32,133	74,811	450,714	(35,052)	(36,646)	485,960
Balance (in shares) at Dec. 31, 2010	30,304,481
Comprehensive income:
Net earnings			65,971			65,971
Other comprehensive income, net of tax					(42,290)	(42,290)
Cash dividends			(15,230)			(15,230)
Stock-based compensation		5,310				5,310
Exercise of stock options	185	7,477		150		7,812
Exercise of stock options (in shares)	188,649
Balance at Dec. 31, 2011	32,318	87,598	501,455	(34,902)	(78,936)	507,533
Balance (in shares) at Dec. 31, 2011	30,493,130
Comprehensive income:
Net earnings			81,857			81,857
Other comprehensive income, net of tax					4,917	4,917
Cash dividends			(16,422)			(16,422)
Tax witholdings paid for net settlement of stock awards		(280)				(280)
Stock-based compensation		7,666				7,666
Issuance of units in connection with Datac acquisition on January 19, 2012	116	8,300				8,416
Issuance of units in connection with Datac acquisition on January 19, 2012 (in shares)	116,716
Equity offering	2,875	214,690	0			217,565
Equity offering (in shares)	2,875,000
Exercise of equity awards	75	2,471		173		2,719
Exercise of equity awards (in shares)	83,505
Balance at Dec. 31, 2012	$ 35,384	$ 320,445	$ 566,890	$ (34,729)	$ (74,019)	$ 813,971
Balance (in shares) at Dec. 31, 2012	33,568,351