We lease various office facilities, equipment and vehicles under operating lease arrangements, some of which contain rent escalation clauses. Most of the leases contain purchase and/or renewal options at fair market and fair rental value, respectively. Rental expense relating to all operating leases was $15.4 million, $15.0 million and $13.6 million in 2017, 2016 and 2015, respectively. At December 31, 2017, future minimum rental payments under noncancelable operating leases are as follows:



	Operating Leases
	(in thousands)
2018	$	15,358
2019	13,849
2020	11,058
2021	8,401
2022	7,236
Thereafter	12,995
Total minimum lease payments	$	68,897