Contractual Obligations and Off-Balance-Sheet Arrangements
We lease a majority of our IBX data centers and certain equipment under non-cancellable lease agreements expiring through 2065. The following represents our debt maturities, financings, leases and other contractual commitments as of September 30, 2018 (in thousands):
Term loans and other loans payable (1)
Senior notes (1)
Capital lease and other financing obligations (3)
Operating leases (4)
Other contractual commitments (5)
Asset retirement obligations (6)
Represents principal and unamortized mortgage premium only.
Represents interest on mortgage payable, loans payable, senior notes and term loans based on their respective interest rates as of September 30, 2018, as well as the credit facility fee for the revolving credit facility.
Represents principal and interest.
Represents minimum operating lease payments, excluding potential lease renewals.
Represents off-balance sheet arrangements. Other contractual commitments are described below.
Represents liability, net of future accretion expense.
In connection with certain of our leases and other contracts requiring deposits, we entered into 42 irrevocable letters of credit totaling $69.1 million under the revolving credit facility. These letters of credit were provided in lieu of cash deposits. If beneficiaries of the letters of credit were to draw down on these letters of credit triggered by an event of default under the lease, we will be required to fund these letters of credit either through cash collateral or borrowing under the revolving credit facility. These contingent commitments are not reflected in the table above.
We had accrued liabilities related to uncertain tax positions totaling approximately $113.2 million as of September 30, 2018. These liabilities, which are reflected on our balance sheet, are not reflected in the table above since it is unclear when these liabilities will be paid.
As of September 30, 2018, we were contractually committed for $760.9 million of unaccrued capital expenditures, primarily for IBX equipment not yet delivered and labor not yet provided in connection with the work necessary to complete construction and open these IBX data centers prior to making them available to customers for installation. This amount, which is expected to be paid during the remainder of 2018 and thereafter, is reflected in the table above as "other contractual commitments."
We had other non-capital purchase commitments in place as of September 30, 2018, such as commitments to purchase power in select locations and other open purchase orders, which contractually bind us for goods or services to be delivered or provided during 2018 and beyond. Such other purchase commitments as of September 30, 2018, which total $789.6 million, are also reflected in the table above as "other contractual commitments."
Additionally, we entered into lease agreements in various locations for a total lease commitment of approximately $230.2 million, excluding potential lease renewals. These lease agreements will commence between April 2019 and August 2019 with lease terms of 10 to 30 years, which are not reflected in the table above.
Critical Accounting Policies and Estimates
Our condensed consolidated financial statements and accompanying notes are prepared in accordance with U.S. GAAP. The preparation of our financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. On an ongoing basis, management evaluates the accounting policies, assumptions, estimates and judgments to ensure that our condensed consolidated financial statements are presented fairly and in accordance with U.S. GAAP. Management bases its assumptions, estimates and judgments on historical experience, current trends