Operating Leases

Most of the Company’s rental properties are leased under operating leases with expiration dates ranging from 1 to 31 years. Future minimum rentals on non-cancelable tenant operating leases at December 31, 2018 are as follows (in thousands):



	Amount
Year:
2019	$	520,139
2020	503,344
2021	492,165
2022	477,671
2023	449,686
Thereafter	3,953,717
Total	$	6,396,722

As of December 31, 2018, the Company had 57 ground leases at its properties. The Company's tenants, who are generally sub-tenants under these ground leases, are responsible for paying the rent under these ground leases. In the event the tenant fails to pay the ground lease rent, the Company would be primarily responsible for the payment, assuming the Company does not sell or re-tenant the property. Future minimum lease payments under these ground lease obligations at December 31, 2018 are as follows, excluding contingent rent due under leases where the ground lease payment, or a portion thereof, is based on the level of the tenant's sales (in thousands):



	Amount
Year:
2019	$	22,867
2020	23,236
2021	23,600
2022	22,996
2023	22,303
Thereafter	257,446
Total	$	372,448

The Company leases its executive office from an unrelated landlord. Rental expense totaled approximately $1.0 million, $1.0 million and $681 thousand for the years ended December 31, 2018, 2017 and 2016, respectively, and is included as a component of general and administrative expense in the accompanying consolidated statements of income. Future minimum lease payments under this lease at December 31, 2018 are as follows (in thousands):



	Amount
Year:
2019	$	856
2020	856
2021	884
2022	967
2023	967
Thereafter	2,658
Total	$	7,188