The Company also invests in equity securities, merger arbitrage securities, investment funds, private equity, loans and real estate related assets. The Company's investments in investment funds and its other alternative investments have experienced, and the Company expects to continue to experience, greater fluctuations in investment income.
Reserves for excess and assumed workers’ compensation business are net of an aggregate net discount of $530 million and $563 million as of December 31, 2019 and 2018, respectively.
Net Investment Income. Following is a summary of net investment income for the years ended December 31, 2019 and 2018:
Casualty reinsurance treaties - The Company purchases casualty reinsurance to reduce its exposure to large individual casualty losses, workers’ compensation catastrophe losses and casualty losses involving multiple claimants or insureds for the majority of business written by its U.S. companies. A significant casualty treaty (casualty catastrophe) in effect as of January 1, 2020 provides significant protection for losses between $5 million and $75 million from single events with claims involving two or more insurable interests or for systemic events involving multiple insureds and/or policy years. The treaty also covers casualty contingency losses in excess of $2 million and up to $97 million. For losses involving two or more claimants for primary workers’ compensation business, coverage is generally in place for losses between $5 million and $270 million. For excess workers’ compensation business, such coverage is generally in place for losses between $25 million and $545 million.
Following is a summary of the Company's contractual obligations as of December 31, 2019:
In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses, which amends the accounting guidance for credit losses on financial instruments. The updated guidance amends the current other-than-temporary impairment model for available-for-sale debt securities by requiring the recognition of impairments relating to credit losses through an allowance account and limits the amount of credit loss to the difference between a security’s amortized cost basis and its fair value. This guidance also applies a new current expected credit loss model for determining credit-related impairments for financial instruments measured at amortized cost, such as reinsurance recoverables. The updated guidance is effective for reporting periods beginning after December 15, 2019.
All other recently issued but not yet effective accounting and reporting standards are either not applicable to the Company or are not expected to have a material impact on the Company.
At December 31, 2019 and 2018, there were no investments, other than investments in United States government and government agency securities, which exceeded 10% of common stockholders’ equity. At December 31, 2019, investments with a carrying value of $1,639 million were on deposit in custodial or trust accounts, of which $1,219 million was on deposit with insurance regulators, $380 million was on deposit in support of the Company’s underwriting activities at Lloyd’s, $36 million was on deposit as security for reinsurance clients and $4 million was on deposit as security for letters of credit issued in support of the Company’s reinsurance operations.
A mixed-use project in Washington, D.C. has been under development in 2019 and 2018.
The following is supplementary information regarding average historical claims duration as of December 31, 2019:
Claims occurring during the current year are net of loss reserve discounts of $20 million, $24 million and $22 million in 2019, 2018, and 2017, respectively.
Income before income taxes from domestic operations was $739 million, $755 million and $797 million for the years ended December 31, 2019, 2018 and 2017, respectively. Income (loss) before income taxes from foreign operations was $114 million, $57 million and $(25) million for the years ended December 31, 2019, 2018 and 2017, respectively.
The Company has a long-term incentive compensation plan ("LTIP") that provides for compensation to key executives based on the growth in the Company's book value per share over a five year period.