Shareholders' Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Other Ownership Interests [Line Items]
Preferred Stock Rights Plan, Description	On July 21, 2005, the Board of Directors adopted a Preferred Stock Rights Plan. Pursuant to the Preferred Stock Rights Plan, we distributed Rights as a dividend at the rate of one Right for each share of our common stock held by shareholders of record as of the close of business on August 12, 2005. The Rights expire on August 12, 2015, unless redeemed or exchanged. The Rights are not exercisable until the earlier of: (1) 10 days (or such later date as may be determined by the Board of Directors) following an announcement that a person or group has acquired beneficial ownership of 20% of our common stock or (2) 10 days (or such later date as may be determined by the Board of Directors) following the announcement of a tender offer which would result in a person or group obtaining beneficial ownership of 20% or more of our outstanding common stock, subject to certain exceptions (the earlier of such dates being called the Distribution Date). The Rights are initially exercisable for one-thousandth of a share of our Series A Preferred Stock at a price of $120 per one-thousandth share, subject to adjustment. However, if: (1) after the Distribution Date we are acquired in certain types of transactions, or (2) any person or group (with limited exceptions) acquires beneficial ownership of 20% of our common stock, then holders of Rights (other than the 20% holder) will be entitled to receive, upon exercise of the Right, common stock (or in case we are completely acquired, common stock of the acquirer) having a market value of two times the exercise price of the Right. Philips Business Electronics International B.V., or any of its affiliates, shall not be considered for the 20% calculation so long as it does not acquire 30% or more of our common shares. We are entitled to redeem the Rights, for $0.001 per Right, at the discretion of the Board of Directors, until certain specified times. We may also require the exchange of Rights, at a rate of one share of common stock for each Right, under certain circumstances. We also have the ability to amend the Rights, subject to certain limitations.
PEO Combination, Description	On February 21, 1997, we acquired substantially all of the assets and liabilities of the electron optics business of Koninklijke Philips Electronics N.V. (the “PEO Combination”), in a transaction accounted for as a reverse acquisition. As part of the PEO Combination, we agreed to issue to Philips additional shares of our common stock whenever stock options that were outstanding on the date of the closing of the PEO Combination are exercised. Any such additional shares are issued at a rate of approximately 1.22 shares to Philips for each share issued on exercise of these options. We receive no additional consideration for these shares issued to Philips under this agreement.
Number of shares authorized to be repurchased	4,000,000
Remaining number of shares authorized to be repurchased	2,140,300
Number of shares repurchased	1,654,400	205,300
Value of shares repurchased	50,000	4,862
Average cost per share of share repurchases	30.19	23.66
Shares reserved for future issuance	4,112,919
Philips [Member]
Other Ownership Interests [Line Items]
Shares issued during period, other	0	0	0
Shares reserved for future issuance	165,000