Temporary investments with an original maturity of three months or less and money market funds with greater than three month maturities but with the right to redeem without notices are treated as cash equivalents and are stated at cost. Temporary investments totaled $3.2 billion and $358 million at September 30, 2021 and December 31, 2020, respectively.

A reconciliation of cash and temporary investments and restricted cash in the consolidated balance sheet to cash and temporary investments and restricted cash in the consolidated statement of cash flows for the nine months ended September 30, 2021 and 2020 is as follows:


	Nine Months Ended September 30,
In millions	2021		2020
Cash and Temporary Investments	$	2,122	$	678
Restricted Cash	1,499		—
Total Cash and Temporary Investments and Restricted Cash	$	3,621	$	678

The Company's restricted cash consists of the cash proceeds from the debt incurred by Sylvamo Corporation as part of the Printing Papers segment spin-off that was completed on October 1, 2021. Of this amount, approximately $1.4 billion was remitted to the Company in the form of a cash distribution. See Note 17 - Debt for further details regarding the Sylvamo debt and the use of the cash proceeds from the debt issuances.


In millions	September 30, 2021		December 31, 2020
Accounts and notes receivable, net:
Trade	$	3,222	$	2,776
Other	327		288
Total	$	3,549	$	3,064

The allowance for expected credit losses was $64 million and $76 million at September 30, 2021 and December 31, 2020, respectively. Based on the Company's accounting estimates and the facts and circumstances available as of the reporting date, we believe our allowance for expected credit losses is adequate.

Inventories


In millions	September 30, 2021		December 31, 2020
Raw materials	$	241	$	268
Finished pulp, paper and packaging	1,156		1,091
Operating supplies	569		627
Other	87		64
Total	$	2,053	$	2,050

Accumulated depreciation was $21.2 billion and $21.4 billion at September 30, 2021 and December 31, 2020, respectively. Depreciation expense was $302 million and $300 million for the three months ended September 30, 2021 and 2020, respectively, and $888 million and $902 million for the nine months ended September 30, 2021 and 2020, respectively.

Non-cash additions to plants, property and equipment included within accounts payable were $61 million and $41 million at September 30, 2021 and December 31, 2020, respectively.

Amounts invested in capital projects in the accompanying condensed consolidated statement of cash flows are presented net of insurance recoveries of $6 million received during the nine months ended September 30, 2021 and $40 million received during the nine months ended September 30, 2020.

Interest payments made during the nine months ended September 30, 2021 and 2020 were $357 million and $520 million, respectively.


	Three Months Ended September 30,				Nine Months Ended September 30,
In millions	2021		2020		2021		2020
Interest expense	$	117	$	148	$	358	$	467
Interest income	24		36		116		122
Capitalized interest costs	3		9		8		27

The Company had recorded liabilities of $135 million and $116 million related to asset retirement obligations at September 30, 2021 and December 31, 2020, respectively.