At the end of each year, differences between the actual return on plan assets and the expected return on plan assets are combined with other differences in actual versus expected experience to form a net unamortized actuarial gain or loss in accumulated other comprehensive income. Only those net actuarial gains or losses in excess of the deferred realized and unrealized appreciation and depreciation are potentially subject to amortization.
The types of items that generate actuarial gains and losses that may be subject to amortization in net periodic pension (credit) cost include the following:
Asset returns that are more or less than the expected return on plan assets for the year;
Actual participant demographic experience different from assumed (retirements, terminations and deaths during the year);
Actual salary increases different from assumed; and
Any changes in assumptions that are made to better reflect anticipated experience of the plan or to reflect current market conditions on the measurement date (discount rate, longevity increases, changes in expected participant behavior and expected return on plan assets).
Amortization of the unrecognized actuarial gain or loss is included as a component of pension credit for a year if the magnitude of the net unamortized gain or loss in accumulated other comprehensive income exceeds 10% of the greater of the benefit obligation or the market-related value of assets (10% corridor). The amortization component is equal to that excess divided by the average remaining service period of active employees expected to receive benefits under the plan. At the end of 2014, the Company had no net unamortized actuarial gains or losses in accumulated other comprehensive income subject to amortization outside the 10% corridor, and therefore, no amortized gain or loss amounts were included in the pension credit in the first six months of 2015.
As a result of the Cable ONE spin-off and KHE Campuses sale, the Company remeasured the accumulated and projected benefit obligation as of July 1, 2015 and September 3, 2015, respectively, and recorded a curtailment gain. During the first six months of 2015, there were pension asset gains and an increase in the discount rate, which resulted in net unamortized actuarial gains in accumulated other comprehensive income subject to amortization outside the corridor, and therefore, an amortized gain of $11.9 million is included in the pension credit for the last six months of 2015. During the last four months of 2015, there were significant pension asset losses that resulted in no net unamortized actuarial gains or losses in accumulated other comprehensive income subject to amortization outside the 10% corridor, and therefore, no amortized gain or loss amounts were included in the pension credit for 2016.
During 2016, there was a decrease in the discount rate and pension asset losses that still resulted in unamortized gains in accumulated other comprehensive income subject to amortization outside the corridor; an amortized gain amount of $4.4 million was included in the pension credit for 2017.
During 2017, there were pension asset gains offset by a further decrease in the discount rate; however, the Company currently estimates that there will be net unamortized gains in accumulated other comprehensive income subject to amortization outside the corridor, and therefore, an amortized gain amount of $4.2 million is included in the estimated pension credit for 2018.
Overall, the Company estimates that it will record a net pension credit of approximately $69 million in 2018.
Note 15 to the Company’s Consolidated Financial Statements provides additional details surrounding pension costs and related assumptions.
Accounting for Income Taxes.
Deferred income taxes arise from temporary differences between the tax and financial statement recognition of assets and liabilities. In evaluating its ability to recover deferred tax assets within the jurisdiction from which they arise, the Company considers all available positive and negative evidence, including scheduled reversals of deferred tax liabilities, projected future taxable income, tax planning strategies and recent financial operations. These assumptions require significant judgment about forecasts of future taxable income.
As of December 31, 2017, the Company had state income tax net operating loss carryforwards of $635.1 million, which will expire at various future dates. Also at December 31, 2017, the Company had $68.4 million of non-U.S. income tax loss carryforwards, of which $57.4 million may be carried forward indefinitely; $7.0 million of losses that, if unutilized, will expire in varying amounts through 2022; and $3.9 million of losses that, if unutilized, will start to expire after 2022. At December 31, 2017, the Company has established approximately $48.7 million in valuation allowances against deferred state tax assets, net of U.S. Federal income taxes, and non-U.S. deferred tax assets, as the Company believes that it is more likely than not that the benefit from certain state and non-U.S. net operating