Consolidated Statements of Shareholders' Equity Statement (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Noncontrolling Interest [Member]
Balances, beginning at Dec. 31, 2008
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Provision for income taxes (Scenario, Adjustment [Member])	$ (1,582)			$ (1,582)
Balances, ending at Dec. 31, 2009 (Scenario, Previously Reported [Member])	185,351	1,210	(1,759)	185,900	0
Balances, ending at Dec. 31, 2009	183,769	1,210	(1,759)	184,318	0
Balances, ending, shares at Dec. 31, 2009 (Scenario, Previously Reported [Member])		62,348,268
Balances, beginning, shares at Dec. 31, 2009		62,348,268
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Provision for income taxes	(24,927)
Provision for income taxes at Jan. 01, 2010 (Scenario, Previously Reported [Member])	(24,754)
Provision for income taxes (Scenario, Adjustment [Member])	(173)
Net income	50,535			50,535
Net income at Jan. 01, 2010 (Scenario, Previously Reported [Member])	50,708
Net income (Scenario, Adjustment [Member])	(173)
Other comprehensive income, change in net unrealized losses from investments, net of tax	547		547
Share-based compensation	4,722	4,722
Payment of cash dividends	(8,646)			(8,646)
Repurchases of common stock, shares		(1,594,089)
Repurchases of common stock	(16,053)	(10,543)		(5,510)
Employee stock transactions, shares		849,981
Employee stock transactions	6,861	6,861
Tax effect of employee stock transactions	151	151
Balances, ending at Dec. 31, 2010 (Scenario, Previously Reported [Member])	223,641			222,452
Balances, ending (Scenario, Adjustment [Member])	(1,755)			(1,755)
Balances, ending at Dec. 31, 2010	221,886	2,401	(1,212)	220,697	0
Balances, ending, shares at Dec. 31, 2010		61,604,160
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Provision for income taxes	(13,742)
Provision for income taxes at Jan. 01, 2011 (Scenario, Previously Reported [Member])	(13,586)
Provision for income taxes (Scenario, Adjustment [Member])	(156)
Net income	33,860			33,860
Net income at Jan. 01, 2011 (Scenario, Previously Reported [Member])	34,016
Net income (Scenario, Adjustment [Member])	(156)
Other comprehensive income, change in net unrealized losses from investments, net of tax	325		325
Share-based compensation	5,886	5,886
Payment of cash dividends	(9,358)			(9,358)
Repurchases of common stock, shares		(1,853,962)
Repurchases of common stock	(20,253)	(20,253)
Employee stock transactions, shares		1,293,571
Employee stock transactions	12,040	12,040
Tax effect of employee stock transactions	195	195
Purchases of common stock for withholding taxes on vested restricted stock, shares		(5,262)
Purchases of common stock for withholding taxes on vested restricted stock	(63)	(63)
Balances, ending at Dec. 31, 2011 (Scenario, Previously Reported [Member])	246,429			247,110
Balances, ending (Scenario, Adjustment [Member])	(1,911)			(1,911)
Balances, ending at Dec. 31, 2011	244,518	206	(887)	245,199	0
Balances, ending, shares at Dec. 31, 2011	61,038,507	61,038,507
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Provision for income taxes	(15,966)
Net income	12,328			12,318	10
Other comprehensive income, change in net unrealized losses from investments, net of tax	355		355
Noncontrolling interest of PhaseLink	977				977
Acquisition of noncontrolling interest in PhaseLink	(932)	55			(987)
Share-based compensation	7,558	7,558
Payment of cash dividends	(12,072)			(12,072)
Repurchases of common stock, shares		(3,431,548)
Repurchases of common stock	(34,551)	(10,742)		(23,809)
Employee stock transactions, shares		599,980
Employee stock transactions	3,642	3,642
Tax effect of employee stock transactions	(185)	(185)
Purchases of common stock for withholding taxes on vested restricted stock, shares		(53,274)
Purchases of common stock for withholding taxes on vested restricted stock	(534)	(534)
Balances, ending at Dec. 31, 2012	$ 221,104	$ 0	$ (532)	$ 221,636	$ 0
Balances, ending, shares at Dec. 31, 2012	58,153,665	58,153,665