CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Capital in Excess of Par Value	Retained Earnings	Treasury Stock
Balance at Dec. 31, 2009	$ 238,293	$ 856	$ 175,224	$ 71,610	$ (9,397)
Balance (in shares) at Dec. 31, 2009		85,600,218			4,988,538
Increase (Decrease) in Shareholders' Equity
Net income and comprehensive income	40,092			40,092
Stock-based compensation cost	7,544		7,544
Exercise of stock options	9,128	27	9,101
Exercise of stock options (in shares)		2,741,328
Excess tax benefit from exercise of stock options	12,581		12,581
Balance at Dec. 31, 2010	307,638	883	204,450	111,702	(9,397)
Balance (in shares) at Dec. 31, 2010		88,341,546			4,988,538
Increase (Decrease) in Shareholders' Equity
Net income and comprehensive income	47,785			47,785
Stock-based compensation cost	8,376		8,376
Equity consideration for the acquisition of HDI	3,799		3,799
Exercise of stock options	12,744	23	12,721
Exercise of stock options (in shares)		2,133,824
Vesting of restricted stock awards and units, net of shares withheld for employee tax	(1,156)		(1,156)
Vesting of restricted stock awards and units, net of shares withheld for employee tax (in shares)		100,467
Excess tax benefit from exercise of stock options	12,051		12,051
Balance at Dec. 31, 2011	391,237	906	240,241	159,487	(9,397)
Balance (in shares) at Dec. 31, 2011		90,575,837			4,988,538
Increase (Decrease) in Shareholders' Equity
Net income and comprehensive income	50,516			50,516
Stock-based compensation cost	9,116		9,116
Purchase of Treasury Stock	(10,617)				(10,617)
Purchase of Treasury Stock (in shares)					436,309
Exercise of stock options	11,973	16	11,957
Exercise of stock options (in shares)		1,673,457
Vesting of restricted stock awards and units, net of shares withheld for employee tax	(1,784)	1	(1,785)
Vesting of restricted stock awards and units, net of shares withheld for employee tax (in shares)		125,245
Excess tax benefit from exercise of stock options	12,433		12,433
Balance at Dec. 31, 2012	$ 462,874	$ 923	$ 271,962	$ 210,003	$ (20,014)
Balance (in shares) at Dec. 31, 2012		92,374,539			5,424,847