Statement of Shareholders' Equity (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stockholders' Equity Attributable to Parent	$ 270,489	$ 221,778	$ 270,489	$ 221,778	$ 185,034	$ 151,131
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures			257	257	289
Net Income (Loss) Attributable to Parent	28,996	6,230	43,865	25,226	27,015
Share-based Compensation			4,001	4,802	5,439
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense			211	528	242
Issuance of Convertible Note				13,963
Adjustments to Additional Paid in Capital, Warrant Issued				7,007
Purchase of convertible note hedge				(14,507)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent			394	(683)	914
Unrealized Gain (Loss) on Investments			(17)	151	4
Additional Paid-in Capital [Member]
Stockholders' Equity Attributable to Parent	409,974	405,505	409,974	405,505	393,456	387,486
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures			257	256	289
Share-based Compensation			4,001	4,802	5,439
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense			211	528	242
Issuance of Convertible Note				13,963
Adjustments to Additional Paid in Capital, Warrant Issued				7,007
Purchase of convertible note hedge				(14,507)
Common Stock [Member]
Shares, Issued	32,367	31,883	32,367	31,883	31,417	30,997
Stockholders' Equity Attributable to Parent	32	32	32	32	31	31
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures			484	466	420
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures			0	1	0
Accumulated Other Comprehensive Income (Loss) [Member]
Stockholders' Equity Attributable to Parent	(1,085)	(1,462)	(1,085)	(1,462)	(930)	(1,848)
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures			0	0	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent			394	(683)	914
Unrealized Gain (Loss) on Investments			(17)	151	4
Retained Earnings [Member]
Stockholders' Equity Attributable to Parent	(138,432)	(182,297)	(138,432)	(182,297)	(207,523)	(234,538)
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures			0	0	0
Net Income (Loss) Attributable to Parent			$ 43,865	$ 25,226	$ 27,015