Income Taxes	9 Months Ended
Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Note 8 — Income Taxes Forrester provides for income taxes on an interim basis according to management’s estimate of the effective tax rate expected to be applicable for the full fiscal year. Certain items such as changes in tax rates and tax benefits related to disqualifying dispositions of incentive stock options are treated as discrete items and are recorded in the period in which they arise. Income tax expense for the nine months ended September 30, 2015 was $5.3 million resulting in an effective tax rate of 34.8% for the period. Income tax expense for the nine months ended September 30, 2014 was $5.0 million resulting in an effective tax rate of 40.7% for the period. The decrease in the effective tax rate for nine months ended September 30, 2015 as compared to the prior year period is primarily due to a $0.7 million tax benefit in the 2015 period related the U.S. Tax Court opinion in the “Altera” case as described below. In addition, the 2015 period includes a $0.3 million loss on the liquidation of a foreign subsidiary in the 2015 period for which a tax benefit could not be recognized, partially offset by a $0.2 million expense in the 2014 period for a U.S. state audit that did not recur in 2015. In July 2015 the U.S. Tax Court issued an opinion in Altera Corp. v. Commissioner related to the treatment of stock-based compensation expense in an intercompany cost-sharing arrangement. The opinion invalidates part of a treasury regulation requiring stock-based compensation to be included in any qualified intercompany cost sharing arrangement. The Company has reviewed this case and concluded that recording a tax benefit of $0.7 million during the three months ended September 30, 2015 was appropriate based on the opinion in the case. The Company will continue to monitor ongoing developments and potential impacts to our consolidated financial statements.

Income Taxes

9 Months Ended

Sep. 30, 2015

Note 8 — Income Taxes

Forrester provides for income taxes on an interim basis according to management’s estimate of the effective tax rate expected to be applicable for the full fiscal year. Certain items such as changes in tax rates and tax benefits related to disqualifying dispositions of incentive stock options are treated as discrete items and are recorded in the period in which they arise.

Income tax expense for the nine months ended September 30, 2015 was $5.3 million resulting in an effective tax rate of 34.8% for the period. Income tax expense for the nine months ended September 30, 2014 was $5.0 million resulting in an effective tax rate of 40.7% for the period. The decrease in the effective tax rate for nine months ended September 30, 2015 as compared to the prior year period is primarily due to a $0.7 million tax benefit in the 2015 period related the U.S. Tax Court opinion in the “Altera” case as described below. In addition, the 2015 period includes a $0.3 million loss on the liquidation of a foreign subsidiary in the 2015 period for which a tax benefit could not be recognized, partially offset by a $0.2 million expense in the 2014 period for a U.S. state audit that did not recur in 2015.

In July 2015 the U.S. Tax Court issued an opinion in Altera Corp. v. Commissioner related to the treatment of stock-based compensation expense in an intercompany cost-sharing arrangement. The opinion invalidates part of a treasury regulation requiring stock-based compensation to be included in any qualified intercompany cost sharing arrangement. The Company has reviewed this case and concluded that recording a tax benefit of $0.7 million during the three months ended September 30, 2015 was appropriate based on the opinion in the case. The Company will continue to monitor ongoing developments and potential impacts to our consolidated financial statements.