Commitments and Contingencies Commitments Letters of credit  The Company had $1.8 million of outstanding letters of credit related to normal business transactions at September 30, 2017 . These agreements require the Company to maintain specified amounts of cash as collateral in segregated accounts to support the letters of credit issued thereunder, which will affect the amount of cash the Company has available for other uses. The amount of cash collateral in these segregated accounts was $12.6 million and $ 10.9 million as of September 30, 2017 and September 24, 2016, respectively, and is reflected in Restricted cash on the Consolidated Balance Sheets. Purchase commitments  Production and purchase agreements (primarily for grass seed and grains) entered into in the ordinary course of business obligate the Company to make future purchases based on estimated yields. The terms of these contracts vary and have fixed prices or quantities. At September 30, 2017 , estimated annual purchase commitments were $104.4 million for fiscal 2018, $31.3 million for fiscal 2019, $18.9 million for fiscal 2020, $11.4 million for fiscal 2021, $4.3 million for fiscal 2022 and $0.8 million thereafter. Leases  The Company has operating lease agreements principally for office and warehouse facilities and equipment. Such leases have remaining terms of one to 12 years . Rental expense was $31.7 million for fiscal 2017, $25.0 million for fiscal 2016 and $23.1 million for fiscal 2015 and is included in cost of goods sold and occupancy or selling, general and administrative expenses in the Company's consolidated statements of operations. Certain facility leases have renewal options and include escalation clauses. Minimum lease payments include scheduled rent increases pursuant to these escalation provisions. Aggregate minimum annual payments on non-cancelable operating leases at September 30, 2017 are as follows: (in thousands) Fiscal year: 2018 $ 26,461 2019 21,393 2020 16,658 2021 12,222 2022 8,812 Thereafter 25,885 Total $ 111,431 Con