8. Leases

Our restaurants are generally operated in leased premises. Lease terms for traditional shopping center or building leases generally include combined initial and option terms of 20-25 years. Ground leases generally include combined initial and option terms of 30-40 years. The option terms in each of these leases are typically in five-year increments. Typically, the lease includes rent escalation terms every five years including fixed rent escalations, escalations based on inflation indexes, and fair market value adjustments. Certain leases contain contingent rental provisions that include a fixed base rent plus an additional percentage of the restaurant’s sales in excess of stipulated amounts. Our leases generally provide for the payment of common area maintenance, property taxes, insurance and various other use and occupancy costs. In addition, we are the lessee under non-cancelable leases covering certain offices.

Contractually required future minimum cash lease payments under existing operating leases as of December 31, 2017 are as follows:



2018	$	281,461
2019		285,264
2020		283,934
2021		279,816
2022		278,615
Thereafter		2,497,163
Total minimum lease payments	$	3,906,253

Minimum lease payments have not been reduced by minimum sublease rentals of $7,359 due in the future under non-cancelable subleases.

Rental expense consists of the following:



	Year ended December 31,
	2017		2016		2015
Minimum rentals	$	278,812	$	255,955	$	227,602
Contingent rentals	$	2,317	$	1,811	$	4,542
Sublease rental income	$	(2,214)	$	(2,074)	$	(1,879)

We have six sales and leaseback transactions. These transactions do not qualify for sale leaseback accounting because of our deemed continuing involvement with the buyer-lessor due to fixed price renewal options, which results in the transaction being recorded under the financing method. Under the financing method, the assets remain on the consolidated balance sheet and the proceeds from the transactions are recorded as a financing liability. A portion of lease payments are applied as payments of deemed principal and imputed interest. The deemed landlord financing liability was $2,630 and $2,854 as of December 31, 2017, and 2016, respectively, with the current portion of the liability included in accrued liabilities, and the remaining portion included in other liabilities in the consolidated balance sheet.