Stock-Based Compensation Plans	6 Months Ended
Jun. 30, 2012
Stock-Based Compensation Plans [Abstract]
Stock-Based Compensation Plans	Note 11 – Stock-based compensation plans Stock option plans Our stockholders approved the 1994 Incentive Stock Option Plan (the “1994 Plan”) in May 1994. At the time of approval, 13,668,750 shares of our common stock were reserved for issuance under this plan. In 1997, an additional 10,631,250 shares of our common stock were reserved for issuance under this plan, and an additional 1,125,000 shares were reserved for issuance under this plan in 2004. The 1994 Plan terminated in May 2005, except with respect to outstanding awards previously granted thereunder. Awards under the plan were either incentive stock options within the meaning of Section 422 of the Internal Revenue Code or nonqualified options. The right to purchase shares under the options vests over a five to ten-year period, beginning on the date of grant. Vesting of ten year awards may accelerate based on the Company’s previous year’s earnings and revenue growth but shares cannot accelerate to vest over a period of less than five years. Stock options must be exercised within ten years from date of grant. Stock options were issued with an exercise price which was equal to the market price of our common stock at the grant date. We estimate potential forfeitures of stock grants and adjust compensation cost recorded accordingly. The estimate of forfeitures will be adjusted over the requisite service period to the extent that actual forfeitures differ, or are expected to differ, from such estimates. Changes in estimated forfeitures will be recognized through a cumulative catch-up adjustment in the period of change and will also impact the amount of stock compensation expense to be recognized in future periods. During the six month period ended June 30, 2012, we did not make any changes in accounting principles or methods of estimates. Restricted stock plan Our stockholders approved our 2005 Incentive Plan (the “2005 Plan”) in May 2005. At the time of approval, 4,050,000 shares of our common stock were reserved for issuance under this plan, as well as the number of shares which had been reserved but not issued under the 1994 Plan (our incentive stock option plan which terminated in May 2005), and any shares that returned to the 1994 Plan as a result of termination of options or repurchase of shares issued under such plan. The 2005 Plan, administered by the Compensation Committee of the Board of Directors, provided for granting of incentive awards in the form of restricted stock and RSUs to directors, executive officers and employees of the Company and its subsidiaries. Awards vest over a three, five or ten-year period, beginning on the date of grant. Vesting of ten year awards may accelerate based on the Company’s previous year’s earnings and growth but ten year awards cannot accelerate to vest over a period of less than five years. The 2005 Plan terminated on May 11, 2010, except with respect to outstanding awards previously granted thereunder. There were 3,362,304 shares of common stock that were reserved but not issued under the 1994 Plan and the 2005 Plan as of May 11, 2010. Our stockholders approved our 2010 Incentive Plan (the “2010 Plan”) on May 11, 2010. At the time of approval, 3,000,000 shares of our common stock were reserved for issuance under this plan, as well as the 3,362,304 shares of common stock that were reserved but not issued under the 1994 Plan and the 2005 Plan as of May 11, 2010, and any shares that are returned to the 1994 Plan and the 2005 Plan as a result of forfeiture or termination of options or RSUs or repurchase of shares issued under these plans. The 2010 Plan, administered by the Compensation Committee of the Board of Directors, provides for granting of incentive awards in the form of restricted stock and RSUs to employees, directors and consultants of the Company and employees and consultants of any parent or subsidiary of the Company. Awards vest over a three, five or ten-year period, beginning on the date of grant. Vesting of ten year awards may accelerate based on the Company’s previous year’s earnings and growth but ten year awards cannot accelerate to vest over a period of less than five years. There were 3,919,146 shares available for grant under the 2010 Plan at June 30, 2012. We estimate potential forfeitures of RSUs and adjust compensation cost recorded accordingly. The estimate of forfeitures will be adjusted over the requisite service period to the extent that actual forfeitures differ, or are expected to differ, from such estimates. Changes in estimated forfeitures will be recognized through a cumulative catch-up adjustment in the period of change and will also impact the amount of stock compensation expense to be recognized in future periods. During the six month period ended June 30, 2012, we did not make any changes in accounting principles or methods of estimates related to the 2010 Plan. Employee stock purchase plan Our employee stock purchase plan permits substantially all domestic employees and employees of designated subsidiaries to acquire our common stock at a purchase price of 85% of the lower of the market price at the beginning or the end of the purchase period. The plan has quarterly purchase periods generally beginning on February 1, May 1, August 1 and November 1 of each year. Employees may designate up to 15% of their compensation for the purchase of common stock under this plan. On May 10, 2011, our stockholders approved an additional 3,000,000 shares for issuance under our employee stock purchase plan, and at June 30, 2012, we had 3,144,521 shares of common stock reserved for future issuance under this plan. We issued 535,617 shares under this plan in the six month period ended June 30, 2012. The weighted average fair value of the employees’ purchase rights was $22.79 per share and was estimated using the Black-Scholes model. During the six months ended June 30, 2012, we did not make any changes in accounting principles or methods of estimates with respect to such plan. Authorized Preferred Stock and Preferred Stock Purchase Rights Plan We have 5,000,000 authorized shares of preferred stock. On January 21, 2004, our Board of Directors designated 750,000 of these shares as Series A Participating Preferred Stock in conjunction with its adoption of a Preferred Stock Rights Agreement (the “Rights Agreement”) and declaration of a dividend of one preferred share purchase right (a “Right”) for each share of common stock outstanding held as of May 10, 2004 or issued thereafter. Each Right will entitle its holder to purchase one one-thousandth of a share of National Instruments’ Series A Participating Preferred Stock at an exercise price of $200, subject to adjustment, under certain circumstances. The Rights Agreement was not adopted in response to any effort to acquire control of National Instruments. The Rights only become exercisable in certain limited circumstances following the tenth day after a person or group announces acquisitions of or tender offers for 20% or more of our common stock. In addition, if an acquirer (subject to certain exclusions for certain current stockholders of National Instruments, an “Acquiring Person”) obtains 20% or more of our common stock, then each Right (other than the Rights owned by an Acquiring Person or its affiliates) will entitle the holder to purchase, for the exercise price, shares of our common stock having a value equal to two times the exercise price. Under certain circumstances, our Board of Directors may redeem the Rights, in whole, but not in part, at a purchase price of $0.01 per Right. The Rights have no voting privileges and are attached to and automatically traded with our common stock until the occurrence of specified trigger events. The Rights will expire on the earlier of May 10, 2014 or the exchange or redemption of the Rights. There were not any shares of preferred stock issued and outstanding at June 30, 2012.

Note 11 – Stock-based compensation plans

Stock option plans

Our stockholders approved the 1994 Incentive Stock Option Plan (the “1994 Plan”) in May 1994. At the time of approval, 13,668,750 shares of our common stock were reserved for issuance under this plan. In 1997, an additional 10,631,250 shares of our common stock were reserved for issuance under this plan, and an additional 1,125,000 shares were reserved for issuance under this plan in 2004. The 1994 Plan terminated in May 2005, except with respect to outstanding awards previously granted thereunder.

Awards under the plan were either incentive stock options within the meaning of Section 422 of the Internal Revenue Code or nonqualified options. The right to purchase shares under the options vests over a five to ten-year period, beginning on the date of grant. Vesting of ten year awards may accelerate based on the Company’s previous year’s earnings and revenue growth but shares cannot accelerate to vest over a period of less than five years. Stock options must be exercised within ten years from date of grant. Stock options were issued with an exercise price which was equal to the market price of our common stock at the grant date. We estimate potential forfeitures of stock grants and adjust compensation cost recorded accordingly. The estimate of forfeitures will be adjusted over the requisite service period to the extent that actual forfeitures differ, or are expected to differ, from such estimates. Changes in estimated forfeitures will be recognized through a cumulative catch-up adjustment in the period of change and will also impact the amount of stock compensation expense to be recognized in future periods. During the six month period ended June 30, 2012, we did not make any changes in accounting principles or methods of estimates.

Restricted stock plan

Our stockholders approved our 2005 Incentive Plan (the “2005 Plan”) in May 2005. At the time of approval, 4,050,000 shares of our common stock were reserved for issuance under this plan, as well as the number of shares which had been reserved but not issued under the 1994 Plan (our incentive stock option plan which terminated in May 2005), and any shares that returned to the 1994 Plan as a result of termination of options or repurchase of shares issued under such plan. The 2005 Plan, administered by the Compensation Committee of the Board of Directors, provided for granting of incentive awards in the form of restricted stock and RSUs to directors, executive officers and employees of the Company and its subsidiaries. Awards vest over a three, five or ten-year period, beginning on the date of grant. Vesting of ten year awards may accelerate based on the Company’s previous year’s earnings and growth but ten year awards cannot accelerate to vest over a period of less than five years. The 2005 Plan terminated on May 11, 2010, except with respect to outstanding awards previously granted thereunder. There were 3,362,304 shares of common stock that were reserved but not issued under the 1994 Plan and the 2005 Plan as of May 11, 2010.

Our stockholders approved our 2010 Incentive Plan (the “2010 Plan”) on May 11, 2010. At the time of approval, 3,000,000 shares of our common stock were reserved for issuance under this plan, as well as the 3,362,304 shares of common stock that were reserved but not issued under the 1994 Plan and the 2005 Plan as of May 11, 2010, and any shares that are returned to the 1994 Plan and the 2005 Plan as a result of forfeiture or termination of options or RSUs or repurchase of shares issued under these plans. The 2010 Plan, administered by the Compensation Committee of the Board of Directors, provides for granting of incentive awards in the form of restricted stock and RSUs to employees, directors and consultants of the Company and employees and consultants of any parent or subsidiary of the Company. Awards vest over a three, five or ten-year period, beginning on the date of grant. Vesting of ten year awards may accelerate based on the Company’s previous year’s earnings and growth but ten year awards cannot accelerate to vest over a period of less than five years. There were 3,919,146 shares available for grant under the 2010 Plan at June 30, 2012.

We estimate potential forfeitures of RSUs and adjust compensation cost recorded accordingly. The estimate of forfeitures will be adjusted over the requisite service period to the extent that actual forfeitures differ, or are expected to differ, from such estimates. Changes in estimated forfeitures will be recognized through a cumulative catch-up adjustment in the period of change and will also impact the amount of stock compensation expense to be recognized in future periods. During the six month period ended June 30, 2012, we did not make any changes in accounting principles or methods of estimates related to the 2010 Plan.

Employee stock purchase plan

Our employee stock purchase plan permits substantially all domestic employees and employees of designated subsidiaries to acquire our common stock at a purchase price of 85% of the lower of the market price at the beginning or the end of the purchase period. The plan has quarterly purchase periods generally beginning on February 1, May 1, August 1 and November 1 of each year. Employees may designate up to 15% of their compensation for the purchase of common stock under this plan. On May 10, 2011, our stockholders approved an additional 3,000,000 shares for issuance under our employee stock purchase plan, and at June 30, 2012, we had 3,144,521 shares of common stock reserved for future issuance under this plan. We issued 535,617 shares under this plan in the six month period ended June 30, 2012. The weighted average fair value of the employees’ purchase rights was $22.79 per share and was estimated using the Black-Scholes model. During the six months ended June 30, 2012, we did not make any changes in accounting principles or methods of estimates with respect to such plan.

Authorized Preferred Stock and Preferred Stock Purchase Rights Plan

We have 5,000,000 authorized shares of preferred stock. On January 21, 2004, our Board of Directors designated 750,000 of these shares as Series A Participating Preferred Stock in conjunction with its adoption of a Preferred Stock Rights Agreement (the “Rights Agreement”) and declaration of a dividend of one preferred share purchase right (a “Right”) for each share of common stock outstanding held as of May 10, 2004 or issued thereafter. Each Right will entitle its holder to purchase one one-thousandth of a share of National Instruments’ Series A Participating Preferred Stock at an exercise price of $200, subject to adjustment, under certain circumstances. The Rights Agreement was not adopted in response to any effort to acquire control of National Instruments.

The Rights only become exercisable in certain limited circumstances following the tenth day after a person or group announces acquisitions of or tender offers for 20% or more of our common stock. In addition, if an acquirer (subject to certain exclusions for certain current stockholders of National Instruments, an “Acquiring Person”) obtains 20% or more of our common stock, then each Right (other than the Rights owned by an Acquiring Person or its affiliates) will entitle the holder to purchase, for the exercise price, shares of our common stock having a value equal to two times the exercise price. Under certain circumstances, our Board of Directors may redeem the Rights, in whole, but not in part, at a purchase price of $0.01 per Right. The Rights have no voting privileges and are attached to and automatically traded with our common stock until the occurrence of specified trigger events. The Rights will expire on the earlier of May 10, 2014 or the exchange or redemption of the Rights.

There were not any shares of preferred stock issued and outstanding at June 30, 2012.