Income Taxes	3 Months Ended
Apr. 01, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The provision for income taxes is determined using an estimated annual effective tax rate, which is generally less than the U.S. federal statutory rate, primarily due to research and development (“R&D”) tax credits and deductions available for domestic production activities. Our effective tax rate may be subject to fluctuations during the year as new information is obtained, which may affect the assumptions used to estimate the annual effective tax rate, including factors such as expected utilization of R&D tax credits, valuation allowances against deferred tax assets, the recognition or derecognition of tax benefits related to uncertain tax positions, and changes in or the interpretation of tax laws in jurisdictions where we conduct business. We recognize deferred tax assets and liabilities for temporary differences between the financial reporting basis and the tax basis of our assets and liabilities along with net operating loss and tax credit carryovers. We record a valuation allowance against our deferred tax assets to reduce the net carrying value to an amount that we believe is more likely than not to be realized. When we establish or reduce our valuation allowances against our deferred tax assets, the provision for income taxes will increase or decrease, respectively, in the period when that determination is made. We recorded income tax expense of $0.4 million (effective tax rate of 15.6%) for the three months ended April 1, 2017 compared to $7.2 million (effective tax rate of 34.6%) for the three months ended April 2, 2016. The decrease in the effective tax rate for the three months ended April 1, 2017 compared to the three months ended April 2, 2016 was primarily due to the preliminary gain on divestitures of our Pittsburgh and Miltec operations of $18.8 million, which resulted in a higher state tax liability, compared to the current year three month period. FASB ASU 2016-09 became effective for us beginning January 1, 2017 and requires all the tax effects related to share-based payments be recorded through the income statement. During the current year three month period, we recognized tax benefits (“windfalls”) from deductions of share-based payments in excess of compensation cost recognized for financial reporting purposes that decreased the income tax expense and effective tax rate. Our total amount of unrecognized tax benefits were $3.4 million and $3.0 million as of April 1, 2017 and December 31, 2016, respectively. If recognized, $2.1 million would affect the effective tax rate. We do not reasonably expect significant increases or decreases to our unrecognized tax benefits in the next twelve months. In 2016, the Internal Revenue Service (“IRS”) commenced an audit of our 2014 and 2015 tax years. Although the outcome of tax examinations cannot be predicted with certainty, we believe we have adequately accrued for tax deficiencies or reductions in tax benefits, if any, that could result from the examination and all open audit years.

Income Taxes

The provision for income taxes is determined using an estimated annual effective tax rate, which is generally less than the U.S. federal statutory rate, primarily due to research and development (“R&D”) tax credits and deductions available for domestic production activities. Our effective tax rate may be subject to fluctuations during the year as new information is obtained, which may affect the assumptions used to estimate the annual effective tax rate, including factors such as expected utilization of R&D tax credits, valuation allowances against deferred tax assets, the recognition or derecognition of tax benefits related to uncertain tax positions, and changes in or the interpretation of tax laws in jurisdictions where we conduct business. We recognize deferred tax assets and liabilities for temporary differences between the financial reporting basis and the tax basis of our assets and liabilities along with net operating loss and tax credit carryovers.

We record a valuation allowance against our deferred tax assets to reduce the net carrying value to an amount that we believe is more likely than not to be realized. When we establish or reduce our valuation allowances against our deferred tax assets, the provision for income taxes will increase or decrease, respectively, in the period when that determination is made.

We recorded income tax expense of $0.4 million (effective tax rate of 15.6%) for the three months ended April 1, 2017 compared to $7.2 million (effective tax rate of 34.6%) for the three months ended April 2, 2016. The decrease in the effective tax rate for the three months ended April 1, 2017 compared to the three months ended April 2, 2016 was primarily due to the preliminary gain on divestitures of our Pittsburgh and Miltec operations of $18.8 million, which resulted in a higher state tax liability, compared to the current year three month period. FASB ASU 2016-09 became effective for us beginning January 1, 2017 and requires all the tax effects related to share-based payments be recorded through the income statement. During the current year three month period, we recognized tax benefits (“windfalls”) from deductions of share-based payments in excess of compensation cost recognized for financial reporting purposes that decreased the income tax expense and effective tax rate.

Our total amount of unrecognized tax benefits were $3.4 million and $3.0 million as of April 1, 2017 and December 31, 2016, respectively. If recognized, $2.1 million would affect the effective tax rate. We do not reasonably expect significant increases or decreases to our unrecognized tax benefits in the next twelve months.

In 2016, the Internal Revenue Service (“IRS”) commenced an audit of our 2014 and 2015 tax years. Although the outcome of tax examinations cannot be predicted with certainty, we believe we have adequately accrued for tax deficiencies or reductions in tax benefits, if any, that could result from the examination and all open audit years.