
11.	LEASES

We lease office space in various buildings for our own use. The terms of these non-cancelable operating leases provide for us to pay base rent and a share of operating expenses and real estate taxes in excess of defined amounts. We also lease equipment under both operating and capital lease arrangements. Minimum future lease payments (e.g., base rent for leases of office space) due in each of the next five years and thereafter, as of December 31, 2017, are presented in the below table.



($ in millions)
2018	$	173.1
2019	158.0
2020	134.6
2021	116.6
2022	87.6
Thereafter	301.0
Total	$	970.9

The total of minimum rentals to be received in the future as sublessor under noncancelable operating subleases was $16.9 million as of December 31, 2017.

Total rent expense, including office space and other rentals, was $197.3 million, $170.4 million and $141.1 million for the years ended December 31, 2017, 2016 and 2015, respectively.