In connection with our recognition of an allowance for credit losses for reinsurance-related assets, we perform a quantitative analysis using a probability of loss approach to estimate expected credit losses for reinsurance recoverables, inclusive of similar assets recognized using the deposit method of accounting. As of March 31, 2021, our allowance for credit losses for reinsurance-related assets was $191 million. There have been no material changes to the allowance for credit losses for the three months ended March 31, 2021.

Some portions of our annuity business have been reinsured on a Modco basis with other companies. In a Modco agreement, we as the ceding company retain the reserves, as well as the assets backing those reserves, and the reinsurer shares proportionally in all financial terms of the reinsured policies based on their respective percentage of the risk. Effective October 1, 2018, we entered into one such Modco agreement with Athene Holding Ltd. (“Athene”) to reinsure fixed and fixed indexed annuity products, which resulted in a deposit asset of $5.6 billion and $5.8 billion as of March 31, 2021, and December 31, 2020, respectively, within other assets on our Consolidated Balance Sheets.

We held assets in support of reserves associated with the transaction in a Modco investment portfolio, which consisted of the following (in millions):


	As of			As of
	March 31,			December 31,
	2021			2020
Fixed maturity AFS securities		$	1,357		$	1,531
Trading securities			3,293			3,357
Equity securities			20			17
Mortgage loans on real estate			875			832
Derivative investments			106			103
Other investments			212			167
Cash and invested cash			81			92
Accrued investment income			39			42
Other assets			6			3
Total		$	5,989		$	6,144

In addition, the portfolio was supported by $175 million of over-collateralization and a $163 million letter of credit as of March 31, 2021.