Future decommissioning costs related to SCE's nuclear assets are expected to be funded from independent decommissioning trusts.

The following table sets forth amortized cost and fair value of the trust investments (see Note 4 for a discussion of fair value of the trust investments):

1	Short-term investments include $59 million and $138 million of repurchase agreements payable by financial institutions which earn interest, are fully secured by U.S. Treasury securities and mature by October 1, 2021 and January 4, 2021 as of September 30, 2021 and December 31, 2020, respectively.

Trust fund earnings (based on specific identification) increase the trust fund balance and the asset retirement obligation ("ARO") regulatory liability. Unrealized holding gains, net of losses, were $1.9 billion and $2.1 billion at September 30, 2021 and December 31, 2020, respectively.

Trust assets are used to pay income taxes arising from trust investing activity. Deferred tax liabilities related to net unrealized gains were $511 million and $515 million at September 30, 2021 and December 31, 2020, respectively. Accordingly, the fair value of trust assets available to pay future decommissioning costs, net of deferred income taxes, totaled $4.3 billion at both September 30, 2021 and December 31, 2020.

The following table summarizes the gains and losses for the trust investments:


	Three months ended September 30,				Nine months ended September 30,
(in millions)	2021		2020		2021		2020
Gross realized gains	$	77	$	51	$	328	$	165
Gross realized losses		(5)		(2)		(21)		(5)
Net unrealized (losses) gains for equity securities		(74)		110		(41)		5

Due to regulatory mechanisms, changes in assets of the trusts from income or loss items have no impact on operating revenue or earnings.

Edison International's Investments

Edison International holds strategic investments in companies focused on developing electric technologies and services. In the second quarter of 2021, one of the investments, Proterra, became publicly traded on the NASDAQ under ticker symbol PTRA. During the three and nine months ended September 30, 2021, Edison International recognized unrealized pre-tax loss of $8 million ($6 million after-tax) and unrealized pre-tax gain of $4 million ($3 million after-tax), respectively, which is reflected as "Other income" on the consolidated statements of income. See Note 16. As of September 30, 2021, the Proterra investment is measured at fair value of $13 million. For further information, see Note 4.