Income Taxes	9 Months Ended
Sep. 30, 2019
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. Our quarterly tax provision, and our quarterly estimate of our annual effective tax rate, is subject to significant variation due to several factors, including variability in accurately predicting our pre-tax and taxable income and loss and the mix of jurisdictions to which they relate, changes in how we do business, changes in our stock price, foreign currency gains (losses), tax law developments (including changes in statutes, regulations, case law, and administrative practices), and relative changes of expenses or losses for which tax benefits are not recognized. Additionally, our effective tax rate can be more or less volatile based on the amount of pre-tax income or loss. For example, the impact of discrete items and non-deductible expenses on our effective tax rate is greater when our pre-tax income is lower. For 2019, the anticipated effective income tax rate is expected to continue to differ from the Federal statutory rate of 21% primarily due to the effect of state income taxes, research and development credits, permanent differences between book and taxable income and certain discrete items. At September 30, 2019, we had total deferred income tax assets ("DTAs") of $47.0 million and no valuation allowance. This reflects an increase of $0.5 million from the December 31, 2018 DTAs of $46.5 million and no valuation allowance. 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) that all or some portion of the DTAs will be realized in the future. During the fourth quarter of each year, we update our multi-year forecast of taxable income for our operations, which assists in analyzing the recoverability of our DTAs.

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.

Our quarterly tax provision, and our quarterly estimate of our annual effective tax rate, is subject to significant variation due to several factors, including variability in accurately predicting our pre-tax and taxable income and loss and the mix of jurisdictions to which they relate, changes in how we do business, changes in our stock price, foreign currency gains (losses), tax law developments (including changes in statutes, regulations, case law, and administrative practices), and relative changes of expenses or losses for which tax benefits are not recognized. Additionally, our effective tax rate can be more or less volatile based on the amount of pre-tax income or loss. For example, the impact of discrete items and non-deductible expenses on our effective tax rate is greater when our pre-tax income is lower.

For 2019, the anticipated effective income tax rate is expected to continue to differ from the Federal statutory rate of 21% primarily due to the effect of state income taxes, research and development credits, permanent differences between book and taxable income and certain discrete items.

At September 30, 2019, we had total deferred income tax assets ("DTAs") of $47.0 million and no valuation allowance. This reflects an increase of $0.5 million from the December 31, 2018 DTAs of $46.5 million and no valuation allowance.

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) that all or some portion of the DTAs will be realized in the future. During the fourth quarter of each year, we update our multi-year forecast of taxable income for our operations, which assists in analyzing the recoverability of our DTAs.