We lease office, retail and storage space to tenants, primarily under non-cancellable operating leases, which generally have terms ranging from five to fifteen years. Most of our leases provide tenants with extension options at either fixed or market rates and few of our leases provide tenants with options to early terminate, but such options generally impose an economic penalty on the tenant upon exercising. Rental revenue is recognized in accordance with ASC Topic 842, Leases, and includes (i) fixed payments of cash rents, which represents revenue each tenant pays in accordance with the terms of its respective lease and that is recognized on a straight-line basis over the non-cancellable term of the lease, and includes the effects of rent steps and rent abatements under the leases, (ii) variable payments of tenant reimbursements, which are recoveries of all or a portion of the operating expenses and real estate taxes of the property and is recognized in the same period as the expenses are incurred, (iii) amortization of acquired above and below-market leases, net and (iv) lease termination income.

	For the Three Months Ended June 30,						For the Six Months Ended June 30,
(Amounts in thousands)	2021			2020			2021			2020
Rental revenue:
Fixed	$	159,641		$	153,868	⁽¹⁾	$	320,270		$	314,544	⁽¹⁾
Variable		14,987	⁽²⁾		10,121			27,504	⁽²⁾		24,870
Total rental revenue	$	174,628		$	163,989		$	347,774		$	339,414

The following table is a schedule of future undiscounted cash flows under non-cancellable operating leases in effect as of June 30, 2021, for the six-month period from July 1, 2021 through December 31, 2021, and each of the five succeeding years and thereafter commencing January 1, 2022.

(Amounts in thousands)
2021	$	320,578
2022		632,390
2023		607,310
2024		580,419
2025		522,620
2026		426,925
Thereafter		2,007,828
Total	$	5,098,070