The Company leases commercial space to the U.S. Government through the GSA or other federal agencies or nongovernmental tenants. These leases may contain extension options that are predominately at the sole discretion of the tenant. Certain of our leases contain a “soft-term” period of the lease, meaning that the U.S. Government tenant agency has the right to terminate the lease prior to its stated lease end date. While certain of our leases are contractually subject to early termination, we do not believe that our tenant agencies are likely to terminate these leases early given the build-to-suit features at the properties subject to the leases, the weighted average age of these properties based on the date the property was built or renovated-to-suit, where applicable (approximately 15.5 years as of March 31, 2021), the mission-critical focus of the properties subject to the leases and the current level of operations at such properties. Certain lease agreements include variable lease payments that, in the future, will vary based on changes in inflationary measures, real estate tax rates, usage, or share of expenditures of the leased premises.

The following table summarizes the maturity of fixed lease payments under the Company’s leases as of March 31, 2021 (amounts in thousands):

	Payments due by period
	Total		2021		2022		2023		2024		2025		Thereafter
Fixed lease payments	$	1,786,411		157,933		190,149		178,205		161,123		149,843		949,158

In August 2020, we entered into a lease agreement for office space in Washington, D.C. to replace our previous sublease that commenced March 2016 and was terminated in March 2021. This new lease commenced in March 2021 and expires in August 2026. We also lease office space in San Diego, CA under an operating lease that commenced in February 2015 and expires in April 2022.

The commenced leases include variable lease payments that, in the future, will vary based on changes in real estate tax rates, usage, or share of expenditures of the leased premises. The Company has elected not to separate lease and nonlease components for its corporate office leases.

As of March 31, 2021, the unamortized balances associated with the Company’s right-of-use operating lease asset and operating lease liability were $1.7 million and $1.9 million, respectively. As of December 31, 2020, the unamortized balance associated with the Company’s right-of-use operating lease asset and operating lease liability for the Company’s two commenced office leases was $0.4 million. The Company used its incremental borrowing rate, which was arrived at utilizing prevailing market rates and the spread on our revolving credit facility, in order to determine the net present value of the minimum lease payments.

The following table provides quantitative information for the Company’s commenced operating leases for the three months ended March 31, 2021 and 2020 (amounts in thousands):

	For the three months ended March 31,
	2021		2020
Operating leases costs	$	149	$	115

In addition, the maturity of fixed lease payments under the Company’s commenced corporate office leases as of March 31, 2021 is summarized in the table below (amounts in thousands):

	Payments due by period
	Total		2021		2022		2023		2024		2025		Thereafter
Fixed lease payments	$	2,017		251		278		277		446		456		309