Income Taxes	9 Months Ended
Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes — Spok files a consolidated U.S. Federal income tax return and income tax returns in various state, local and foreign jurisdictions as required. At September 30, 2016, we had total deferred income tax assets ("DTAs") of $77.8 million and no valuation allowance. This reflects a change from the December 31, 2015 balance of deferred income tax assets of $129.8 million and a valuation allowance of $45.8 million resulting in an estimated recoverable amount of $84.0 million. The change from December 31, 2015 to September 30, 2016 reflects the expected usage of the deferred income tax assets to offset expected 2016 taxable income, changes in tax rates and a write off of our valuation allowance of $45.8 million against DTAs of the same amount as explained below. During the three months ended September 30, 2016, the US Court of Appeals for the Second Circuit affirmed a Tax Court Decision, unrelated to Spok, regarding the allocation of cancellation of debt income to tax attributes for a company that filed a Federal consolidated income tax return. This impacted the ultimate realization of certain of our net operating loss ("NOL") carryovers. Therefore, during the three months ended September 30, 2016, we wrote off our valuation allowance of $45.8 million against the impacted NOL DTAs. This had no impact on our income tax provision or net income. We consider both positive and negative evidence when evaluating the recoverability of our DTAs. The assessment is required to determine whether based on all available evidence, it is more likely than not (i.e., greater than a 50% probability) whether all or some portion of the DTAs will be realized in the future. During the fourth quarter of each year, we prepare a multi-year forecast of taxable income for our operations which assists in analyzing the recoverability of our DTAs. The anticipated effective income tax rate is expected to continue to differ from the Federal statutory rate of 35% primarily due to the effect of state income taxes, the effect of changes to the DTA valuation allowance, permanent differences between book and taxable income and certain discrete items. As of September 30, 2016, approximately 85% of our DTAs of $77.8 million relate to NOL carry forwards available to offset future taxable income. We no longer have an annual Section 382 limitation on our remaining NOLs.

Income Taxes — Spok files a consolidated U.S. Federal income tax return and income tax returns in various state, local and foreign jurisdictions as required.

At September 30, 2016, we had total deferred income tax assets ("DTAs") of $77.8 million and no valuation allowance. This reflects a change from the December 31, 2015 balance of deferred income tax assets of $129.8 million and a valuation allowance of $45.8 million resulting in an estimated recoverable amount of $84.0 million. The change from December 31, 2015 to September 30, 2016 reflects the expected usage of the deferred income tax assets to offset expected 2016 taxable income, changes in tax rates and a write off of our valuation allowance of $45.8 million against DTAs of the same amount as explained below.

During the three months ended September 30, 2016, the US Court of Appeals for the Second Circuit affirmed a Tax Court Decision, unrelated to Spok, regarding the allocation of cancellation of debt income to tax attributes for a company that filed a Federal consolidated income tax return. This impacted the ultimate realization of certain of our net operating loss ("NOL") carryovers. Therefore, during the three months ended September 30, 2016, we wrote off our valuation allowance of $45.8 million against the impacted NOL DTAs. This had no impact on our income tax provision or net income.

We consider both positive and negative evidence when evaluating the recoverability of our DTAs. The assessment is required to determine whether based on all available evidence, it is more likely than not (i.e., greater than a 50% probability) whether all or some portion of the DTAs will be realized in the future. During the fourth quarter of each year, we prepare a multi-year forecast of taxable income for our operations which assists in analyzing the recoverability of our DTAs.

The anticipated effective income tax rate is expected to continue to differ from the Federal statutory rate of 35% primarily due to the effect of state income taxes, the effect of changes to the DTA valuation allowance, permanent differences between book and taxable income and certain discrete items.

As of September 30, 2016, approximately 85% of our DTAs of $77.8 million relate to NOL carry forwards available to offset future taxable income. We no longer have an annual Section 382 limitation on our remaining NOLs.