Our leased assets include offices and studios, transmitter locations, antenna sites, tower and tower sites or land. Our current lease portfolio has remaining terms from less than up to twenty years. Many of these leases contain options under which we can extend the term for five to twenty years. Renewal options are excluded from our calculation of lease liabilities unless we are reasonably assured to exercise the renewal option. Our lease agreements do not contain residual value guarantees or material restrictive covenants. We lease certain property from our principal stockholders or trusts and partnerships created for the benefit of the principal stockholders and their families. These leases are designated as Related Party leases in the details provided.

Operating leases are reflected on our balance sheet within operating lease ROU assets and the related current and operating lease liabilities. ROU assets represent the right to use an underlying asset for the lease term, and lease liabilities represent the obligation to make lease payments arising from lease agreement. Operating lease ROU assets and liabilities are recognized at the commencement date, or the date on which the lessor makes the underlying asset available for use, based upon the present value of the lease payments over the respective lease term. Lease expense is recognized on a straight-line basis over the lease term, subject to any changes in the lease or expectation regarding the terms. Variable lease costs such as common area maintenance, property taxes and insurance are expensed as incurred.

The adoption of ASC 842 resulted in recording a transitional adjustment to operating lease ROU assets and operating lease liabilities of $65.0 million and $74.4 million, respectively. The difference between the operating lease ROU assets and operating lease liabilities at transition represented existing deferred rent expense and prepaid rent that was derecognized upon adoption. During the six month period ended June 30, 2019, we recorded additional ROU assets and corresponding lease liabilities of $1.1 million.

Future minimum lease payments required under leases that have initial or remaining lease terms in excess of one year as of June 30, 2019, are as follows:

Future minimum lease payments under leases that had initial or remaining lease terms in excess of one year as of December 31, 2018, based on the former accounting guidance for leases, were as follows: