Significant Accounting Policies Quantifying Prior Year Misstatements (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended				12 Months Ended			12 Months Ended										12 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Scenario, Previously Reported [Member]	Dec. 31, 2010 Scenario, Previously Reported [Member]	Dec. 31, 2009 Scenario, Previously Reported [Member]	Dec. 31, 2011 Scenario, Adjustment [Member]	Dec. 31, 2010 Scenario, Adjustment [Member]	Dec. 31, 2009 Scenario, Adjustment [Member]	Dec. 31, 2012 Retained Earnings [Member]	Dec. 31, 2011 Retained Earnings [Member]	Dec. 31, 2010 Retained Earnings [Member]	Dec. 31, 2009 Retained Earnings [Member]	Dec. 31, 2011 Retained Earnings [Member] Scenario, Previously Reported [Member]	Dec. 31, 2010 Retained Earnings [Member] Scenario, Previously Reported [Member]	Dec. 31, 2009 Retained Earnings [Member] Scenario, Previously Reported [Member]	Dec. 31, 2009 Retained Earnings [Member] Scenario, Adjustment [Member]	Dec. 31, 2011 Retained Earnings [Member] Scenario, Adjustment [Member]	Dec. 31, 2010 Retained Earnings [Member] Scenario, Adjustment [Member]	Dec. 31, 2012 Income Tax Receivable [Member] error	Dec. 31, 2010 Deferred Tax Asset Write-Off [Member]	Dec. 31, 2011 Deemed Dividends From Foreign Subsidiaries [Member]	Dec. 31, 2010 Deemed Dividends From Foreign Subsidiaries [Member]	Dec. 31, 2011 Accrued Interest [Member]	Dec. 31, 2010 Accrued Interest [Member]	Dec. 31, 2012 Liquidating Dividends [Member] foreign_subsidiary	Dec. 31, 2012 Income Tax Receivable Pertaining to Research and Development Credits [Member]	Dec. 31, 2012 Income Tax Receivable Related to Share-based Compensation [Member]
Quantifying Misstatement in Current Year Financial Statements, Amount																						$ 180	$ 55	$ 55	$ 97	$ 62	$ 198	$ 1,500	$ 260
Number of closed foreign subsidiaries																											2
Number of balance sheet calculation errors																					2
Balance Sheet Related Disclosures [Abstract]
Income taxes receivable	4,090	6,837	6,701		6,881	6,547		(44)	154
Short-term deferred income taxes	19,811	23,202	25,110		22,854	25,022		348	88
Total current assets	200,116	232,468	214,604		232,164	214,362		304	242
Long-term deferred income taxes	16	6,396	7,739		8,657	9,740		(2,261)	(2,001)
Total assets	281,454	308,018	300,694		309,975	302,453		(1,957)	(1,759)
Long-term income taxes payable	2,759	6,404	5,660		6,450	5,664		(46)	(4)
Total liabilities	60,350	63,500	78,808		63,546	78,812		(46)	(4)
Retained earnings	221,636	245,199	220,697		247,110	222,452		(1,911)	(1,755)
Total shareholders’ equity	221,104	244,518	221,886		246,429	223,641		(1,911)	(1,755)
Total liabilities and shareholders’ equity	281,454	308,018	300,694		309,975	302,453		(1,957)	(1,759)
Income Statement [Abstract]
Provision for income taxes	15,966	13,742	24,927		13,586	24,754		156	173	1,582								1,582
Net income	12,328	33,860	50,535		34,016	50,708		(156)	(173)		12,318	33,860	50,535
Basic (dollars per share)	$ 0.21	$ 0.55	$ 0.81		$ 0.55	$ 0.82		$ 0.00	$ (0.01)
Diluted (dollars per share)	$ 0.20	$ 0.54	$ 0.81		$ 0.55	$ 0.81		$ (0.01)	$ 0.00
Statement of Other Comprehensive Income [Abstract]
Net income	12,328	33,860	50,535		34,016	50,708		(156)	(173)		12,318	33,860	50,535
Comprehensive income	12,673	34,185	51,082		34,341	51,255		(156)	(173)
Statement of Stockholders' Equity [Abstract]
Net income	12,328	33,860	50,535		34,016	50,708		(156)	(173)		12,318	33,860	50,535
Stockholders' Equity Attributable to Parent	$ 221,104	$ 244,518	$ 221,886	$ 183,769	$ 246,429	$ 223,641	$ 185,351	$ (1,911)	$ (1,755)		$ 221,636	$ 245,199	$ 220,697	$ 184,318	$ 247,110	$ 222,452	$ 185,900		$ (1,911)	$ (1,755)